MTN NO SERVICE

I have bought a new Samsung S8 with a new contract from MTN 2018/02/02, i have recieved the phone and start using it, but the phone is restarting and going into restarting loops randomly even when im not using it, apps keep on stoping randomly even when im not using it. I contacted MTN but i keep put through to the same people who keeps telling me to calling MTN Direct, when i call MTN Direct i still reach MTN, i have sent emails and messaged MTN on facebook but no one has contacted me. It is more than 2 months that i try to get a responce or someone to phone me or an email to contact someone from MTN. The Level of service of MTN has degraded. if i dont get an answer or contact soon ill canctle my contract and move to a other service provider