Electronic Money Institutions

We've a client who runs his own business. For banking, accounts etc he uses a service called ANNA. He'd like to start paying into a pension but hasn't been able to find a D2C provider that would help so we have agreed to assist. A few of the platforms have said no because ANNA isn't FSCS registered and/or because ANNA is a payment provider not a bank. The account has a sort code and account number. Anyone found a provider that will accept payments from EMIs like ANNA?