UPGRADE AND OTP

I'm not happy with MTN contact center, (Upgrade Department), I've been struggling to get my phone been upgraded, I've been taken from pillar to post, I've been calling several times all the agents who was assisting they are all failing to assist me, so In this case i don't know if I will ever be assisted by my Network service provider or what? i need answers because i cannot call MTN call center every day and I'm not been helped. secondly I'm not getting OTP when iStore are trying to help me with my upgrade and again your agents are failing to assist me on that as well. I'm not happy with the service that I'm getting with your call center agent.