ETF Question!

Hello all,

     I was just wondering if I switched over would I have to pay the ETF once I got the bill out of pocket and then send in the forms to get a reimbursement for my ETF payment or would T-Mobile be able to get the money to me in time after I send in the appropriate forms to pay the ETF with the card. Just wondering because this will make or break the deal!

                                                                           Thanks.