PAC CODE-question - complicated!

Where to start! I was with GiffGaff (O2) but was getting lousy reception at home so had a look at coverage maps to make a change. I found a great deal with ID Mobile and the Three coverage was rated Good instead of Poor so I signed up. I received my new SIM very quickly and gave my PAC code to ID Mobile to bring over my old number which I’ve had for about 20 years or more. I then tried the phone and found that the coverage was even worse with Three than it was with O2. I cancelled the new contract within days, and at least three days before the PAC code was due to be used by ID Mobile. I then went back and re set up an account with GiffGaff only to find that the PAC code transfer had been carried out despite cancelling the contract days before - so I had to do a new account not just carry on as before. They said the only way was to get a new PAC code from ID Mobile which I duly did - but because the transfer was never completed, and despite cancelling well before the transfer date, the PAC code related to a new number given to me by ID and not my old number. It seems my old number has now disappeared into the ether but I would really like to get it back but am at a loss as to how to do this. Help!