Poor service

I am a 6 year customer with MTN but for the last year and a half i have been receiving bad services from them. They have blacklist my phone while i am still busy paying for my phone on contract, they can't give an explanation why they blacklisted my phone. I also had problems with them to upgrade on my contact whenni was due. They had many stories before i could upgrade. I will not recommend MTN as a service provider as they deliver poor services to long term customers