Keep my old O2 number

[Mony]

Hi
I have tried to contact O2 customer service but I got no help with the automated answer voicemail. I have also tried O2 store twice abd they declined to help me saying I should contact customer services.I hope I can any advice here .
I am an O2 customer for about 3 yrs. I got a Deal to upgrade my phone through a third party using O2 and asked to keep my number. They sent a new 5G sim with a new number and Now I gave 2 I2 numbers abd 2 pay monthly bills.
How can I solve this problem please?

[MI5 · Accepted solution]

@Mony 

You'll need to call customer service to migrate your old number to the new contract..

That will end your old contract Guide: Migration & porting into O2  
Numbers here Guide: Coronavirus Community Help and Support 
Or advice from an O2 Guru regarding a way to get through:
If you call 202, when it comes to the reason you are calling stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to someone.
Say "Upgrade", "Lost/Stolen" or "Fraud" if you have to, to get put through to someone.