Thanks for your post and for reaching out the Community Forums, rubyray,
Your direct debit date for you handset can be changed, however this change will usually not take place for the next direct debit but the one after that. You can also view your entire length of your payment schedule through your online account, for more information about freestyle have a look here
If you are still needing help getting this changed let us know.
Cheers,
Corey C