Bad Service provider

I switched to MTN hoping to get better reception and change my number without keeping the old one form my previous service provider. However every time someone calls me my number automatically goes to voicemail while my device is on. I have tried calling the call centre to find out if anything can be done about my problem. today the call centre agent did not even bother to assist me in anyway but told me to switch my phone off and on and see what happens. At this point I regret switching networks.