Cancel contract and release my number

I have been having billing issues with this service provider since renewal of my other contract in October 2015. I also have connectivity problem in most areas I go to. (Had no network the whole Christmas vacation while everyone in other networks has). I decided not renew my other number rather port it to another network. I was kindly given a form to fill in, when I follow-up a week later I was told it takes 21 days to cancel and release the number. in the meantime my bill was increased almost by +50% of the bill while I was still paying for the handset. On day 21 I call again and this time, the lady says they do not have a record on the system so I must go to one of the shops to cancel, then cancellations/retentions will start the process. <br> I cannot stay another month or even a day with this net work as I am not happy at all with their service. Their smses to remind me to renew my contract are driving me mad.