Poor or no customer service

I am a client of MTN for 16years. My account was suspended. I made a payment immediately, and tried to call to guve proof of payment and have my line reconnected, seeing that I use my phone primarely for business. My clients cant get hold of me etc. I called more than 10 times, held on the line for more or less 3 hours in total. No one answers, I only hear music playing. Still no answer. I also tried to mail, mails return to my mailbox as unsent, because their mailbox is full. How on earth should I get hold of them??