DEBIT ORDER DATE CHANGE

hi<br> <br> i have requested my debit order date to be changed to the 20th of each month and even filled out a form but it wasnt changed .I went to Just Gym for the second time and filled out a form but the debit order wasnt changed AGAN.On my third attempt I filled up a form and i was promised that the debit order will definately change,but guess what??? the debit order was changed to the 15th instead of the 20th.