charge but still no servie

Well if been struggling with mtn overcharging me for the last year.i work away 9 month out of the year, came back this year had over 700 free min then got a message i have exceeded my calling limit how do i do that with 700 min still left they credited my account early the 31st but still no service still cant call 141 all i get is they got technical difficulties what the hell mtn stop ripping people of.let me know what you are gone do abiut this problem or i will stop my debit orders for contract breaching.