Hi @kit98 ,
Thanks for raising this to us, we're sad to know that you're having issues with the mobile service. Here is an article that you may find helpful, this will guide you a basic trourbleshooting to fix the incoming/outgoing call and SMS problem with mobile.
Let us know how it will go.
I’ve just changed to TPG but could not make any calls or receive any calls as well as SMS. My mum had the same issues but she changed phones. However, i do not have any spare phones to try and also i checked that this happened a lot when you changed to TPG. Please advice on how to fix this issue. Thanks