How to Switch from Prepaid to MVNO Postpaid While Keeping Your Number
by selpl Editorial Team
How to Switch from Prepaid to MVNO Postpaid While Keeping Your Number
Once you've settled into life in Korea, prepaid phone (pay-as-you-go) charges can start to feel wasteful. You want to use more data, but you have to watch your balance every time you top up, and talk time and texts are limited. When you switch to an MVNO (mobile virtual network operator) postpaid plan while keeping your existing number, this process is called "number portability." This article addresses the specific points where foreigners typically get stuck in this process.
3 Things You Must Confirm Before Number Portability
Number portability itself is a straightforward procedure, but the following 3 items vary from person to person and carrier to carrier. If you brush over them thinking "it'll all be the same," you'll hit a wall at the application stage.
1. Identity Verification Method The identification document you used to open your prepaid phone (foreigner registration card, passport, etc.) and the verification method required for postpaid conversion differ by carrier and sales outlet. Some also require additional verification such as SMS authentication through your own phone number or credit card confirmation. It's most accurate to check what documents are needed with the carrier or outlet where you plan to apply in advance.
2. Remaining Residence Period and Contract Terms Postpaid plans may have a minimum usage period (contract commitment) depending on the carrier and product. If your remaining residence period is short but you choose a plan with a long commitment, you may face penalties later. Since contract terms vary by product, you must check the conditions before signing up.
3. Whether Your Current Device Supports the New Network The network you'll connect to after number portability will be one of KT, SK, or LG. If your original SIM card or device isn't unlocked or is locked to a specific carrier, it may not work properly on the new network. Since this also varies by device and carrier combination, it's safer to check device compatibility before just swapping out your SIM card.
Number Portability: General Process
- Choose your desired MVNO carrier and plan (confirm whether you'll use KT, SK, or LG network)
- Prepare your ID and required documents (requirements vary by carrier, so check in advance)
- Apply for "number portability" online or at a store—your existing prepaid number is maintained as-is
- Receive and activate your new SIM card; your existing prepaid service is usually automatically terminated at the time of activation (confirm with your carrier)
Plan Comparison: For Light Data Users
If you've just switched from prepaid and mainly use calls and texts with minimal data needs, compare the products below.
| Carrier | Plan | Monthly Cost | Data | Calls | Messages | Network |
|---|---|---|---|---|---|---|
| KTM Mobile | M Budget 1.5GB 100min | ₩5,500 | 1.5GB | 100min | 100 msgs | KT |
| LG Hello Mobile | DATA Worry-Free SIM 1GB | ₩12,900 | 1GB + reduced-speed data | Unlimited (extra 300min) | Unlimited | LG |
| SK Telecom | Easy S | ₩15,950 | 1GB + reduced-speed data | 200min | 200 msgs | SK |
Source: selpl plan database, as of 2026-09-27. Subject to change by carrier policy.
The "reduced-speed data" mentioned here is an option that lets you continue using the internet at lower speeds even after your basic allowance runs out. It's suitable for KakaoTalk messages and text-based web browsing, but video playback or map apps may lag.
Plan Comparison: For Moderate to Heavy Data Users
Once you've settled in, you'll likely use more data for video calls, video streaming, and remote work internet. In these cases, consider plans with larger data allowances that maintain reasonable speeds even after the basic amount is exhausted.
| Carrier | Plan | Monthly Cost | Data | Calls | Messages | Network |
|---|---|---|---|---|---|---|
| KTM Mobile | 5G M Budget 10GB | ₩13,900 | 10GB | Unlimited (extra 50min) | Unlimited | KT |
| SK Telecom | Light 45 | ₩17,000 | 8GB + speed-limited data | Unlimited (extra 300min) | Unlimited | SK |
| LG Hello Mobile | DATA Worry-Free SIM 10GB | ₩25,000 | 10GB + speed-limited data | Unlimited (extra 300min) | Unlimited | LG |
Source: selpl plan database, as of 2026-09-27. Subject to change by carrier policy.
The speeds maintained by "speed-limited data" vary by product. For example, Light 45 maintains speeds suitable for low-quality YouTube playback after your basic data runs out, while higher-tier plans support HD video streaming and video calls without issues. Check the plan's detailed conditions for exact speed information.
FAQ
Q. Can I keep my prepaid number while switching to postpaid? Yes, you can. This is called "number portability," and your number is maintained even when switching carriers and service types (prepaid to postpaid). However, the application method and required documents differ by carrier, so check in advance.
Q. Can I keep using the SIM card from my prepaid phone? No. When you do number portability, you'll usually need to replace your SIM with one compatible with your new carrier and plan. Your number will remain the same even after the SIM change.
Q. Can I use a postpaid plan if I don't have much residence time left? Some plans may have contract commitments (minimum usage periods), so it's important to match your remaining residence period with the contract term. Whether a plan has no contract or a specific commitment period varies by carrier and product, so you must confirm before signing up.
Q. Can I sign up for a postpaid plan with just my ID? The documents needed for identity verification vary by carrier and sales channel (online/store). Some require additional authentication beyond a foreigner registration card, so it's best to confirm directly with your carrier before applying.
Summary
Number portability itself is a straightforward process of keeping your number while switching to postpaid billing. However, since identity verification methods, remaining residence period and contract terms, and device network compatibility vary by product, it's safe to confirm these before applying. Compare plans matching your data usage and budget using the tables above, choosing between KT, SK, and LG networks.
Common Questions
Q. What happens after I apply for number portability? First, choose your desired MVNO carrier and plan among KT, SK, and LG networks, then prepare the ID and documents required by each carrier. After applying for number portability online or at a store, your existing prepaid number is maintained, and the process is complete once you receive and activate your new SIM.
Q. What happens to my prepaid service after number portability? Your existing prepaid service is usually automatically terminated at the time you activate your new SIM. However, the process may vary by carrier, so confirm before applying.
Q. What do "reduced-speed data" and "speed-limited data" in the plan table mean? These are options that let you continue using the internet after your basic data allowance runs out. However, the maintained speeds vary by product, ranging from speeds suitable only for KakaoTalk or text web pages to speeds supporting YouTube low-quality playback, HD video streaming, and video calls.
Q. Can I keep using my current SIM and device on the new network? Not necessarily. If your current device isn't unlocked or is locked to a specific carrier, it may not work properly on the KT, SK, or LG network you'll switch to. It's safer to check whether your device supports the new network before changing your SIM.