Locked sim and being billed for it

I got the fixed mtn sim last week Tuesday. Not informed prior as to which router is supported. Phoned in and told my Huawei b313 is not supported even then I was never told which router to use. Ended up having to buy another router Huawei e525 and still be told it's not supported then i was sent an SMS to state what router the mtn fixed sim is recommended yet I've wasted money already. Then I opted for a cancellation cause ive already lost money only to be told I need to give a 1 months notice. My sim is locked so why should I pay for a service that I'm not using. This whole issue could have costed me nothing had I been given the options in the first place. I am not liable for dec as the sim is locked