waiting one month

Id taken a 3G data contract a month ago. I was told I have coverage in my area but when I got home I realized that Internet speeds were similar to that of ten years ago. I immediately complained to the store who referred me to the call centre who referred me back to the store. I then tried calling the call centre for DAYS and eventually got through. I'd spoken to a supervisor who said she would get back to me but only got back to me when I sent her an email stating my disgust at her pathetic service. She then said she would put my query on priority. I asked to speak to her supervisor nevertheless. She said she would get him to call me. I haven't heard from either of them since even though I've sent her TWO emails asking for feedback .I am currently paying for a service I'm not using and would normally cancel but I stood in a bank queue to get bank statements and stood in a store queue to get a contract. I've spent time to sign a contract and I expect service. Please assist