Bad customer service

i had a contract with Nashua,when they closed down i was moved to MTN. the contract package i had with Nashua I received R200 airtime, 200mb data&25 sms's,&if the airtime was finished i could get them to load an extra amount. But when i was moved to MTN, they gave me an open line which i didnt want. i called, emailed requesting that i be taken to a TOP UP package since they were unable to keep my bill at the same amount i was paying at Nashua. After my move to MTN my bill has just gone crazy.In February i asked that i be migrated to TOP UP, but this wasn't actioned. in April i went to The Glen to do the migration again&this time it was successful.Then end of April i received an invoice of R974 and May i received an invoice of R1711, which i requested my bank to reverse as i was supposed to be on a TOP UP. i have been trying to contact the call centre but since they are on strike i haven't been assisted. how can i have such a high invoice when i am on a TOP UP package. i am willing to pay the TOP UP amount for both months but i am not getting any assistance.On the 12th June i received an sms suspending my line.i have sent Mutshinyani Matodzi emails, no response.