Switching Carriers with Number Portability: Complete Guide to Cheaper Plans
by selpl Editorial Team
Switching Carriers with Number Portability: Complete Guide to Cheaper Plans
If you find your current carrier's rates expensive, you can consider number portability to switch carriers while keeping your phone number. This method lets you transfer to a cheaper plan without having to re-register services connected to your phone number, like your phone number and KakaoTalk.
What is Number Portability?
Number portability means switching to a carrier (MNO like KT, LG U+, or SK Telecom) or a budget carrier (MVNO) while keeping your existing phone number. Since your number doesn't change, you won't need to re-register apps like your bank app or various authentication services.
3 Things to Confirm Before Number Portability
Foreign residents typically encounter obstacles in three areas when attempting number portability. Since conditions vary by carrier and plan, be sure to contact the carrier directly before applying.
1) Identity Verification Documents Which documents can be used for identity verification—such as a foreigner registration card or passport—varies by carrier and plan. Even with the same carrier, offline stores and online signup may require different documents.
2) Remaining Residence Period and Contracts The available plans and contract conditions may differ based on how much time remains on your residence permit. This also varies by carrier and plan, so if your residence period is short, it's safer to inquire before signing up.
3) Whether Your Current Phone Supports the New Carrier's Network The plans shown in the comparison table below use either KT, SK, or LG networks. Whether your current phone supports the new carrier's network varies by device model and carrier/plan, so if you're planning to just swap the SIM card, check network compatibility first.
Budget Plan Comparison
Here are the lowest-priced plans based on light usage.
| Carrier | Plan | Monthly Fee | Data | Calls | SMS | Network |
|---|---|---|---|---|---|---|
| KTM Mobile | M Budget 1.5GB 100min | ₩5,500 | 1.5GB | 100min | 100 msgs | KT |
| KTM Mobile | M Budget Secure 2.5GB | ₩9,500 | 2.5GB+low-speed | Unlimited (add'l 30min) | Unlimited | KT |
| LG Hello Mobile | DATA Worry-Free SIM 1GB | ₩12,900 | 1GB+low-speed | Unlimited (add'l 300min) | Unlimited | LG |
| SK Telecom | Light 39 | ₩12,500 | 6GB+low-speed | Unlimited (add'l 300min) | Unlimited | SK |
| SK Telecom | Easy S | ₩15,950 | 1GB+low-speed | 200min | 200 msgs | SK |
Source: selpl Rate Plan Database, as of 2026-10-11. Subject to change per carrier policy.
These plans are characterized by lower monthly fees in exchange for smaller data allowances. If you don't use many calls or texts, plans with set basic minutes and messages like KTM Mobile's "M Budget 1.5GB 100min" are also an option.
Plan Comparison for Heavy Data Users
If you use significant data for video streaming or work, compare the plans below.
| Carrier | Plan | Monthly Fee | Data | Calls | SMS | Network |
|---|---|---|---|---|---|---|
| The One Mobile | TOP 7GB Basic (Millie's Library) | ₩22,000 | 7GB+low-speed | Unlimited (video·add'l 300min) | Unlimited | KT |
| The One Mobile | TOP 10GB Basic (Millie's Library) | ₩26,400 | 10GB+low-speed | Unlimited (video·add'l 300min) | Unlimited | KT |
| SK Telecom | Light 55 | ₩24,500 | 15GB+low-speed | Unlimited (add'l 300min) | Unlimited | SK |
| SK Telecom | Light 59 | ₩27,500 | 24GB+low-speed | Unlimited (add'l 300min) | Unlimited | SK |
| SK Telecom | Light 69 | ₩28,750 | 110GB+low-speed | Unlimited (add'l 300min) | Unlimited | SK |
Source: selpl Rate Plan Database, as of 2026-10-11. Subject to change per carrier policy.
Even at similar price points, data allowances differ significantly by carrier. For example, SK Telecom's Light 69 in the same late-20,000 won range offers far more data than The One Mobile's TOP plan. It's best to compare based on your typical usage.
"What Happens When I Use Up My Basic Data?"
The low-speed data mentioned in plan descriptions means your internet connection stays active even after you use your basic allowance. However, speeds slow significantly, making KakaoTalk messages and light web browsing possible, but video streaming or large file downloads may lag. Since speed reduction levels vary by plan, if you frequently watch videos, it's better to choose a plan with a generous basic data allowance.
How Does Number Portability Work?
The signup method and required procedures vary depending on whether you sign up online or visit a store, and which carrier/plan you choose. Both MNOs (KT, LG U+, SK Telecom) and MVNOs (budget carriers) support number portability, but for accurate information on specific documents and procedures, contact your desired carrier's customer service or official channels.
Frequently Asked Questions (FAQ)
Q. Can I do number portability if my residence period is ending soon? It depends on the carrier and plan. If your residence period is short, it's safer to contact the carrier directly before signing up to confirm.
Q. Can I do number portability to a budget carrier (MVNO)? Yes. Budget carriers like KTM Mobile, The One Mobile, and LG Hello Mobile also accept number portability signups. They operate by leasing networks from KT, SK, or LG.
Q. Can I keep using my current phone? It depends on whether your device supports the new carrier's network (KT/SK/LG). Even the same phone model may have different support by carrier, so confirmation before signup is necessary.
Q. Will I incur early termination fees with number portability? It depends on your contract terms with your current carrier. If you have remaining contract time, you may face early termination fees, so check your contract status with your current carrier first.
Since identity verification methods, residence period conditions, and device compatibility all differ by carrier and plan, rather than deciding based solely on the prices in the table, it's most reliable to contact the carrier directly before signup to confirm conditions.
Frequently Asked Questions
Q. Will my phone number change if I do number portability? No. Number portability keeps your existing phone number while only changing carriers. You won't need to re-register your bank app or authentication services.
Q. Will my internet disconnect if I use up my basic data? No. Once you use your basic allowance, you switch to low-speed data and speeds slow significantly, but KakaoTalk messages and light web browsing remain possible. However, video streaming or large file downloads may lag.
Q. If two plans are at similar price points, do they offer similar data amounts? No. Even at similar prices, basic data allowances can differ significantly by carrier. For example, among plans in the late-20,000 won range, SK Telecom's Light 69 offers far more data than The One Mobile's TOP plans. Compare based on your typical usage.
Q. Is the number portability application process the same for all carriers? No. Required documents and procedures differ depending on whether you sign up online or visit a store, and which carrier/plan you choose. While both MNOs (KT, LG U+, SK Telecom) and MVNOs (budget carriers) support number portability, you should confirm the exact procedures with your chosen carrier's customer service or official channels.