Why my supplier stop my Switch?

I try so many times to switch from TOTO electricity to bulb but why they don’t let me. They told me just after I pay my debts I am free to go. In fact I did that before with Solarplicity Energy and I received the same “treatment”. I pay all my debts but they didn’t let me to pick myself my new electricity supplier which I like(bulb). Why is happening that to me? Why they scam me?