Although I have adequate credit I am unable to make a call from my cell phone why ?
I checked your call logs and it shows that last call went through. There were couple of calls that didn't go through since number was temporary not available. It might happen when number is busy.
If you still have trouble reaching a number and you know it's not busy then could you please provide exact called number/date/time to customer service and they can check with carriers what is the issue.
Customer Service: https://support.skype.com/faq/FA1170