Unable to use my cellphone properly for over a month since my return from the UK.

I returned home from the UK on 30 Aug. My cellphone on MTN Prepaid was set to "International roaming SMSs only". When I got to SA, I could not disable this option. For the following month I first went to several MTN stores and spent countless hours with consultants there. Eventually one did a SIM card exchange which did not solve the problem. I have phoned MTN customer services repeatedly, and eventually have had individual attention from 2 helpful consultants, Dylan and Abegail, who assured me that the matter had been escalated to "technical ". After "technical" got involved, for a week or so I could receive calls, but COULD NOT MAKE CALLS. So a further complaint, more work by "technical" and NOW I CAN MAKE CALLS BUT NOT RECEIVE CALLS. As I write this, on 1 Oct, that is the position as it has been for the last 2 weeks. In other words my cellphone is STILL not working properly. When I put the SIM card into 2 other phones, they had the same problem! The latest advice from '"technical" is to "reboot" the phone. My problems are: - which phone? apparently no phone will work with this SIM card. - also my Samsung Galaxy Note 8, which is my current in use phone, does not have a "reboot" option, only a "reset" option, which will reset the phone to the original manufacturers status. This entails backing up everything first, and I just do not know how to do this. in any case am not sure that this will work. My current status on the query is waiting for a further reply from "technical" to Abegail. The query number is REQ ***. Please can a "technical" manager contact me, and help me to resolve the problem OR Should I port my number to another service provider? Please note: you cannot call me on the cellphone number below, as it does not receive calls. Please call me on landline ***, or email at ***