Do you have a complaint outstanding, or showing in your account as recently closed?

They stopped doing this during the pandemic but have now re-started this more recently: if you have status and have a complaint pending - sometimes you may not know this if you haven't checked, but it can be that the IFM or IFL has raised one for you - then CR will call to discuss this and then a few days later an email will arrive. Yes, it's a Birmingham number since they are using an outsourced telephony provider and they are from Birmingham. If you look on the main whinge threads there are occasional references to this happening.

It could be a survey or a hospitality invitaiton but they are more usually done by email. They also do unsolicited calls if they are trying to create space in WTP and want to entice you into CW or another service.