Issue receiving calls

Hi, I have a bit of an unusual issue. Today my GP surgery phoned me 4 times and left a voicemail after one of the calls but I have no missed calls or any voicemails.
interestingly my mum’s cancer nurse said she tried calling her a few times today and also couldn’t get through, was getting the engaged tone even though mum wasn’t using her phone. Got through on the landline.
so we both had issues today with NhS numbers not actually getting through.
any ideas?

It's worth checking for any issues in your area on the network status checker TinaB5. If there is nothing going on, come back and let me know.