Disloyal company with bad service

I had so many hassles doing upgrade being a customer for over 10 years, eventually passed credit check. Now the hold up is debit mandate, I've been dealing with branch, emailed customer service, emailed complaints, no1 at mtn gives a damn, how can I receive a new mandate when I have an existing 1, you guys yourself confirmed via email that I will be debited 1 dec, yet I still cannot complete my upgrade and collect new contract n phone, this is how MTN treats loyal customers, no1 gives a d.a.m.n, you guys took 100s of thousands over these last 10 years yet give me such grief and bad service, really don't know what to do anymore, I'm angry for being loyal to MTN. My no is 0.7.3.8.0.8.8.7.8.2