ACCESS TO OLD NUMBER!!

So I had stoped using my old phone number last christmas althought im now having great difficulty trying to fix my apple account on my phone as i need a verifcation code.To use my phone properly at all!Ive went to the apple shop and they say the only soultion is to get my old number back.And ive been chatting to the smarty webchat and they claim thta my old number was never registered with them when it was.Any advise please?