First of all, the amount of the certificate will be used as a prepayment (the maximum possible one, based on the amount of the certificate and the cost of the desired device), this will reduce the total value of the contract, and as a result, the amount of the monthly payment will also be reduced. If the amount of the certificate is less than the amount of the minimum prepayment, then it will be used to cover the first monthly payment for the selected device under the Contract Phone service.