Can't Call Certain Numbers

[#1]

We have a very strange problem with our home phone which has only started today.  I am unable to call certain numbers i.e. my mobile, Husband’s mobile and my parents but I can call other numbers.  If I try and call my house from my mobile it comes up saying number not in use.
Any help/suggestions.

[#2]

Hi,  Had the same last night.  Could only get through to local numbers but mobile and long distance numbers were barred

[#3]

Oddly, I could get through to some local numbers but no all?  It started working then stopped again but seems ok this morning.  Very odd!!

[#4]

Very strange.... it does sound like this was an isolated problem but do let us know if you see this happen again please/
Adam