MTN- HIGHLY DISSATISFIED!!!!!!

So this is not the first time I’m writing about this! MTN has deducted over R2000 from my account even though the account has been paid in cash. They have received countless emails phone calls bank statements etc. there is apparently no higher management that you can speak to directly, only via email. Then I submitted all documentation and only received R351.72 how pathetic. Please, if anyone knows how I can resolve this or get through to higher management I would appreciate it.