Chose my contract for me

14 May 2020 I did a upgrade. Chose a R299 package. The person who did the upgrade made sure that I wanted the R299 deal and I confirmed. Without my consent he changed it to R349 and without informing me. I pay my account manually so I always paid R299 as I agreed to. A month ago after struggling to get invoices, I saw online that my contract was R349 and not R299. I have fallen behind on my account because of that and they suspended my account. I did pay the outstanding although this was not my fault. But can’t use my phone because of the suspension. This has been going on for a week now that I can’t do anything on my phone because of a decision someone else made for me without informing me. How can a service provider choose your contract for you?