Ownership transfer

I've just purchased a refurbished Dell Precision 5530 from a Dell partner in the UK.

I wanted to transfer ownership, so went through this page https://www.dell.com/support/assets-transfer/uk/en/ukbsdt1/#/Identify

I entered my service tag, but unfortunately, I was using a completely different Dell machine at the time.

I didn't realise Dell would immediately associate the service tag I'd entered to the machine I was using without confirming this was correct.

So now whenever I try to transfer ownership, when I enter the service tag from my new Precision, Dell thinks I'm transferring ownership of an Optiplex 3020!

I need to have the service tag reset so I can enter it again for the correct machine.

Does anyone know how I can get that done in the UK? I've tried web chat but they can't do it for me.

Thanks,

Damian