Switching from Contract to Sim only Issues

I have switched to sim only plan after my contract  contract ended  a month ago. I was sent a new SIM card which I don’t need (and have since misplaced) as I want to keep my old number. So far it looks like my new plan has not been transferred to my old sim. I have gone into the ID mobile app to see if I can sort this out, but could not find any such option. The app does show the new plan though. I have tried contacting customer support via their number with no luck. Even tried using the online chat which takes me to a useless chatbot. I am frustrated, seething and feel trapped by the new contract. This is the worst customer support I’ve ever seen on earth. Once ID mobile  knows the money is rolling in, that’s it, you are on your own, it’s on to the next new customer. It doesn’t take a genius to know that business grows by nurturing old customers like us. Every new customer turns to an old one eventually by the way. DEAR ID MOBILE “Please please ID mobile do something about your customer support . It’s not about what the problem is, it’s about how you make customer support easily accessible to your valuable customers. So all I’m asking for is to be able to switch from contract to Sim only seamlessly’’. Any help will be appreciated.Thank you.