This is a continuation of the many threads about Skinny VoLTE availabilty.

My particular configuation is a TCL 403, which I chose because it was the cheapest unlocked smartphone in The Warehouse in March 2025, and a skinny sim, because I thought that it was slightly less likely to turn very expensive than the other pricing model.

For other TCL 403 holders, to exercise the issue, go to:
- Settings / Mobile network / Preferred network type
- choose 4G only
- observe that you continue receiving text messages, but not voice calls
...
- Edit: In the same place, select 3G/4G (auto) to continue receiving voice calls until 3G switchoff

I went through a long switchover support journey where people told me that there were settings to change, but they couldn't or wouldn't tell what they were.

The Warehouse demonstrated that it did 4g just fine, with no settings changed, with someone else's SIM.

Skinny produced the following clear answer:

 

While VoLTE is enabled by default on our SIM cards, its support depends on device compatibility, network configurations, and agreements with handset manufacturers. As a value-focused brand, Skinny currently has a more limited scope for VoLTE support to keep costs low and maintain affordable pricing. However, Spark, our parent brand, has prioritised enabling VoLTE across a wider range of devices.

 

I have received consent to forward the email.

So, as I read the answer, Skinny 4G mobile service is incompatible with the concept of an unlocked handset.

Edit: added recovery instruction.