Awaiting letter for code to change Tax Agent for PAYE

We have changed our payroll provider, they have sent the request on line to become our agent. With this process a code is issued and sent to us by letter, we then need to give our new provider that code so they can apply to become our new agent. We have not yet received this letter and I was wondering if there is a way to escalate this as our agent will not be able to make FPS returns on our behalf until we receive and pass on this code.

Hi Fiona White,
The standard timescale to receive an activation code from HMRC is 10 days within the UK.
If you have not received it within this timescale please contact our Online Services Helpdesk on 0300 200 3600.
Technical support with HMRC online services
Thank you,