How is selling you something on credit 'anticompetitive'?
This makes it blatantly obvious to the consumer that the unsubsidized phones are cheaper.
If they are "selling you the phone on credit", then it would be obvious to require (a) in bill, separate items for the telecommunications and for the phone payment; (b) in advertising, note the full price of the phone, including the all monthly payments+interest; (c) when the phone is paid in full (24 months?), then stop charging for it... rather than continuing the same bill forever.