Why T-Mobile still charged me after i paid payment arrangement before its due ?

Hi !

So, I setup a payment arrangement and then I paid the first,half before the due date and TMOBILE still charged  me ? 

Does the company not understand that people are living paycheck-to-paycheck. Life happens ! 

Having a phone is mandatory in today's world because every service demands it ? 

ANYWAYS!!! I did call customer service and the rep  said " it's best not to make partial payments /pay anything ,  if you set up a payment plan because the system will not cancel it. " 

And THEY DID NOT REFUND ME EITHER FOR THE DOUBLE CHARGE. They just applied it to what I owed. Mad slick .

Then also, Even tho I put a block on TMOBILE they still somehow got around and finesse their way to double charge me.

I remember when , any payment made would cancel a payment arrangement.