Terrible service and i need to pay? No go!

I subscribed for a wifi modem t R199 pm. I called customer care a week after i came home from where i bought it in the Bridge PE. The modem just dies. Of for good. I take out the battery end then sometimes it gows on again and if it is on then it dies every half an hour and i need to take out battery then switch on and wait for connection then i can use it for about 30 min. Today it is off! Not even to charge it or taking battery out helps. I am going to cancell my subscription for this wifi even if it is a contract. I am not paying for something i can not use. I am changing my bank acc nr.