Need to change mobile number on my broadband account

Hi

I have recently taken a new virgin media broadband package. I would like to change the mobile number registered to my account as I have got a new phone number. I tried to check my virgin media account but there is no option to change the mobile number. I have been on the customer care phone for a long time but I have been kept on hold. 

Is there a way to change my mobile number quickly?

Thanks

Venkata