Is this the offer you're referring to? It does require that you have an eligible rate plan on your account, either T-Mobile ONE or a Simple Choice with Unlimited High Speed plan.
Once you've been placed on the appropriate plan, trade in your 6, port in a new line of service from another carrier, and purchase 2 iPhones on an EIP, you will qualify for the rebate. This offer is reimbursed via a prepaid MasterCard, not bill credits. Once you fulfill the qualifications, You'll need to submit a rebate using promo code 18Q3APPLE online at T-Mobile Promotions.
Apple launched the iPhone 8 and iPhone 8 Plus. Both mobiles are good to compare then the others. The technology of the mbile is also good. You can simply upgrade the iPhone 8 to iPhone 8 Plus. You can use any type of accounting software. You can also use the iPad.