Credit agreement information for Handset Loan

My last two payments for my phone loan repayment have not gone through. When I called Virgin Media and o2 about this, no one has any recollection of my loan agreement. I have been able to log in and find out how much I have left to pay, however, it says that I am in arrears and that I need to call 789 from my Virgin number (which is now o2 so no longer works). This is very frustrating.... I'm not sure who I must pay as everyone contacted have no record of this loan. Anyone else struggling with this?