Recovery of gateway ID

Hi. My client wishes to register for the Custom Declaration Service which requires a gateway ID. Unfortunately several have been registered by the company and advisers and it is not clear which one has been used before in this context. The helpline staff will not tell our client the gateway id or the email associated with the service. So my question is (a) is it possible to get a list of all ID's associated with a company and their email address or (b) otherwise how do they resolve this issue? Thanks 

Name removed admin .

Hi Patrick,
Traders need to use the government gateway account which is linked to their EORI.
We would advise contacting the Customs and International trade helpline:
Imports and exports: general enquiries
For more help and for issues with online gateway account please contact our Technical support helpline. 
Technical support with HMRC online services
Thank you.