Blocked call still coming through on my Iphone

Hi all

My blocked call option seems to work for all but one number! It's a spam call that claims to come from Madrid, I've tried all the fixes mentioned in other queries.

I'm completely updated

There are no updates under the carrier

I've switched off and rebooted the phone

I've taken the block off, rebooted, and then re-blocked.

No matter what I try this number still gets through.

I can't block all unknown numbers as I need to get calls from people I may not know for work purposes, I just don't want this number calling me persistently!

I would really appreciate being able to stop this spam call from coming through to my phone and I can't understand why nothing I do seems to work.......