Disappointed at MTN

I have a home WiFi with MTN which I took 2 years ago on a contract and ever since I have never missed a payment , the WiFi is or supposedly unlimited data however today I got the most shocking information from the so called MTN champions and also connected to the supervisor that I have exhausted my data usage whereas there’s absolutely nothing different I did in terms of using the WiFi , normally it’s connected to three cellphones plus the tv and that’s how it has been all along and today am being told that my data is exhausted like really ????? Am thinking to myself is this a method of getting me to upgrade within a blink of an eye not that I was planing to cancel it but after this experience with my WiFi not fully operational am definitely sure that I’ll be cancelling it as the contract term date is next month , they need to make sure that my device works perfectly as I have stated there was nothing different or different activities I have never ever heard of data being exhausted ever since I’ve had this WiFi