Complaint Review: Smart Pay

We bought an iphone 7s from Metro PCS in December. We have excellent credit. The sales clerk suggested instead of putting it on charge card , use "SMART PAY". We could make payments over a period of time, no interest auto withdraw from our checking. We received no follow  up paperwork or emails from Smart Pay . I went to the email address on my bank statements to see what i owed and noticed it is leasing the phone with 11 payments! I called them and was told I had 90 days to pay it off since I didn't pay it off last week I now get 20% added  , have to make the 11 payments and now my $669 phone will be costing me  $1139   Superviser said she could'nt alter the computer since it had already "rolled over"  SMART PAY  REAlly  i SAY smart scam.