SOLD CONTRACT THAT I CANT ACCESS OR ENJOY BENEFITS

Kindly assist me with the matter problem I have with MTN, the sold me a Sim-only contract with number *** that is ineffective, it will have a balance of more than 10gig and notify it ran out of data. I purchased this data when I was busy with my exams in November and explained I need to help with my studies which I use a lot google, whatsApp and telegram and social media at large. they promised they will listen to the call of sale and come back to me, I sent them twitter, emailed them and made numerous (more than 10hrs of phone calls) phone calls but no one is willing to assist me. MTN refuse to cancel contract that i'm not enjoying the benefits. I even asked they replace a contract with one that works but refuse they tell me I was sold music and u-Tube. I don't need such.