So is virgin's credit based on the amount per month you pay? If so this is stupid. I got turned down for a phone on EE - I really wouldn't have cared but I have been paying £109 a month for the past 24 months and I was on the annual upgrade program!. In the end I came from EE to here - paid EE off £809 - and paid £579 for my own phone - being on a mere £20 a month contract I doubt I would ever get something from VM either -(as I am also a Media customer, in my case £51 a month cable) but some advice friend, try and get the phones outside of the network if you can?
The P20 Pro is about £499 from appliance direct and others - can you afford that? You get an unlocked phone and then cheap airtime like you have had - with no commitment. Just an idea.
Pretty sure virgin media can do something about it. The only reason that credit level increase is not approved is because of virgin media payment history. And the VM payment history is erratic due to vm giving me the run around when it was time to renew media contract. Which left an outstanding balance on my account each month. At the time, I took a resolution of a discount on monthly payment. And complaint was ended. Waited on vm sorting my account out. Until finally I paid the outstanding account to stop the automated mail I was recieving each month. And the services being suspended. A due to me cancelling my DD due to vm trying to take £90+ per month when I myself and vm advisor agreed a much lower monthly amount.