Trapped into a contract

Hello, hope someone here can help me as the customer service so far has been telling me that they solved my problem when in fact they did nothing, so about a month ago I decided to get a 24 month contract, I got the sim quiet fast, I installed it and guess what, no service at home or work, I used the chat function and complained about this and they told me to get a new sim as the one I got might be damaged, went straight away to Curry’s and got a new sim and that did not help at all, so I went back to the chat service and complained, I asked for my contract to be canceled as I can’t use their services at all, I’ve been told that it will take a day or two for my contract to be changed from 24 month to Pay as GO and I will be able to cancel then, as it was the weekend I thought it might take a bit longer, well 3 weeks have passed and my contract has not changed, I tried to get in touch with them several times but every time the chat “losses connection” and I am being put in a que that lasts for hours, is there anything I can do? this is soooo frustrating as I got my number trapped and I am paying for something I can’t even use, I can’t even listen to music on spotify and unless I connect to Wi-Fi I can’t even make or receive phone calls. I feel like I’ve been lied to and trapped into a contract when I asked for it to be cancelled twice.