Can't make a call!

I have been with Virgin Mobile for many years and currently have 2 contracts with them. We had no problems until now. I can't make calls between the 2 contracts that I have and it is not the phone settings. We have put the sim card in another phone and the problem is still there. The call immediatly end before connecting and we are struggling with this problem for 2 months now and the Virgin Mobile contact centre can't sort it out. I feel like canceling both contracts.