Has this always happened please?
What happens when they try to cal you?
Only recently. They are given the message " your number is ***** recognised"
I'm guessing that maybe you have actived anonymous caller rejecting which rejects calls from people's phones not sending their caller ID.
Please try this.
On your phone, dial *#227#
You will hear the status if this is active.
If active, please try to temporarily turn this feature off by dialling
Then ask one of the people to call you. Can they now get through?
There is another possibility that you have activated "Last call barring". This webpage details this.
However the symptom to the caller is that they get an engaged tone which you're not reporting.
If this problem still isn't resolved then you will need to escalate it to Talktalk's troublshooting team.
Don't dial their 0870 number as it's costly but rather call this number
Tell the person that answers your call, that you have a fault that needs to be escalated and investigated by their "switch" team. They are the people who troubleshoot when certain calls aren't passed through to your landline.
Please let me know how it goes and I wish you a Merry Christmas!