MTN CALLS NOT COMING THROUGH TO TELKOM NUMBER

I have gradually stopped being able to receive calls from ANY MTN numbers and some other numbers (including Vodacom) I reported it to the store and they said I must dial a number... And fancy that the call didn't go through as the line was down... I then spoke to a consultant who said I must dial a code and it too did not work... How do I fix this I have three months left on my contract and I'm seriously considering canceling . I originally thought that the issue was limited to MTN numbers but have since had complaints from other networks. If they cannot provide the VERY basic service of receiving calls, then they must release me from my contract! I ported from MTN in 2019 as i moved to Telkom. I am losing business and this is completely unacceptable!