Bad client service

We had this 4mbps slow and buffering connection. Paying every month, but in the meantime fiber got installed, only after exploring fiber options we realized they are offering Fiber at way cheaper than this 4mbps line. We never received any better offerings from them, they just pocket the higher payment. On cancelation they requested a written notice which we did but you need to confirm a return mail from them and then only they will cancel. They don't have a customer/client relationship.