Debt that I am not willing to pay

Some time in 2020 I registered for data Sim online on monfo from mtn, Sim card was delivered unfortunately it was not the Sim I ordered I wanted a Sim card to use on my phone and the d I was given was a Sim that goes in the router. I couldn't use the mtn Sim everytime I had to call the call center to help me.... I got tired and I called them for cancelation they told me I can't cancel I'll be bridging a contract. And now am handed over to collection for a d I never used am now expected to pay 1500 for services I never used