Electrician didn't turn up, number is not in use, no response on messaging

Can someone tell me how to secure either a reliable rebooking or a refund in respect of an EICR inspector who didn’t turn up. The number supplied for the electrician is dead and I can’t find any kind of contact for OpenRent.
The company OpenRent assigned the business to have 100% of 1* reviews on Trustpilot, all of which makes it rather unnerving that O.R. trouser the full fee in advance.
Where to next?

contact OpenRent directly. You’ll find their contact details on the help pages at the very bottom IIRC.