Talksure not easy to make contact with

I write this complaint on behalf of my elderly father. He was issued with a gap cover policy a few years ago, but seems to be unaware of it. He has taken out medical gap cover since then with Stratum, and wishes to keep that going. He has been unsuccessful at cancelling this Talksure policy for the last few years. He has no paperwork or membership card to prove his belonging to the institution.

Can someone please contact my father and take his instruction to cancel this policy seriously.