Never received a Decision Letter or a new BRP

I had an appointment for my BRP on the 7th of October 2020 whereby I submitted my request for a new BRP and did all the procedures. I was told to wait for the next 8-10 weeks to receive my decision letter and BRP.
Note that I have already returned my old BRP.

But now, even 90 days after the appointment, I am yet to receive either my decision letter or my BRP.
I don't know what to do or whom to contact.

According to the official website I need to have a decision letter to report that my BRP has not arrived.
[https://www.gov.uk/biometric-residence- ... ot-arrived]

Any suggestions to who I should contact about this or what steps I can take will be greatly appreciated.