Sick of MTN's Poor service

I was phoned on the 8th of August and was offered the 20G for R149 monthly on my main contract number as i spend a lot of money on Data monthly, this is 10G daytime and 10G nighttime data. This sounded quite good and i agreed. This morning when the courier delivered the sim instead of just one simcard i received 2, one which will have 10G - 5G daytime and 5G nighttime the other sim card the same. I have been trying all morning to have this sorted however i have been transferred from pillar to post, no one seems to be able to assist me. I have been given the number of the initial company who phoned me with the offer Umhlanga PTY LTD, guess what, i have been holding for over 30 minutes at a time......NO one is answering the phones!!! This is quite ridiculous and SO SO FRUSTRATING!!! Meaning if no one answers my query will NOT be resolved!