I don’t know if this already exists and I’ve posted something similar before but given that some switchers are really spooked out by calls from PP how about this during the switch process?
“You may receive a call from Pure Planet when you switch to us. If we call you this will be to ask if you have any problems with your switch, or we may ask for clarification if we spot any issues. The caller will ask you a couple of basic security questions, if you are not happy to answer these the caller will offer an alternative way to reassure you that the call has come from Pure Planet.
Please tick this box if you are happy to receive these calls. (I’m not sure, does data protection mandate that you have to opt in, if not it could be please un-tick if you don’t want to receive these calls?)