Why Your Phone Stops Sending Texts or Making Calls After a SIM Swap
When a phone refuses to send texts or make calls right after a SIM swap, the cause is usually clear once you check a few key points. New activation rules, VoLTE requirements, and damaged SIM readers create most failures.
Quick Summary
- Activation delays with Spark, One NZ, or 2degrees block calls and texts.
- New Zealand’s 3G shutdown requires proper 4G/5G VoLTE settings.
- Misaligned SIM insertion can bend SIM reader pins.
- Some models allow SIM reader replacement; many need board repair.
- Blocked IMEI, carrier lock, or baseband faults also mimic SIM problems.
SIM Activation Issues
After a SIM swap, New Zealand carriers require the network to register the new SIM ID. Spark, Vodafone/One NZ, and 2degrees often have delays that block texts and calls until activation completes. Even eSIM migrations trigger the same waiting period.
VoLTE Requirements After NZ 3G Shutdown
When the device is set to 3G-preferred mode or VoLTE is off, the phone fails registration during a SIM swap. It drops straight into SOS-only or No Service. Many overseas models hide or restrict VoLTE, which worsens this problem.
Incorrect SIM Insertion and Reader Damage
Many users misalign the SIM, insert it upside down, or push the tray in while the SIM is sitting above the lip. The force bends the internal SIM reader pins. The device may briefly detect the SIM, then drop out again. These bent pins cannot recover on their own.
Devices Where Reader Replacement Is Possible
- Samsung A-series
- Oppo, Xiaomi, Vivo, and similar mid-range models
Devices That Require Board-Level Repair
- iPhone (all series)
- Samsung S/Note/Flip/Fold
- Google Pixel
These models have SIM readers soldered to the main board. Damage requires micro-soldering, pad reconstruction, or complete board repair.
Faulty SIM Cards
A brand-new SIM can still malfunction. Some faulty SIMs allow mobile data but block SMS, or send texts but fail calls. Testing with a second SIM card confirms this quickly.
IMEI Blocking and Carrier Lock Issues
If the device is IMEI-blocked due to unpaid overseas contracts or a lost/stolen report, calls and texts fail regardless of the SIM. Imported phones with carrier lock behave similarly. The phone reads the SIM but refuses to register with a foreign network.
Baseband or Modem IC Failure
A SIM swap often triggers a reboot, and this exposes failing modem chips. Symptoms include “Searching,” unstable connection, missing IMEI, or “Unknown Baseband.” These issues need proper board-level diagnosis.