Hi Eddy. Together energy aren’t known for their professionalism and they have the opportunity to block someone leaving. It isn’t legal but it does happen. In fact Iresa power were absolutely hammered by OFGEM and have now ceased trading for doing exactly that. If I was you I would but in a complaint to together energy to resolve. Failing that contact OFGEM. The MPAN stuff is nonsense there are no reasons why together can legally block a switch.