Find promotion codes for T-Mobile phones and services at the T-Mobile website under the Shop drop-down menu, as of 2015. The Deals tab brings you to a page where the current promotions are located.
Promotion codes for T-Mobile may offer a free bonus item with purchase or discounts on phones, accessories or service plans. Promotion codes may be limited to certain geographical areas, new customers or only offered for a limited amount of time. The promotion codes are a combination of numbers and letters and are mentioned in the advertisement, and some can only be used when making a web-based purchase and are not valid in T-Mobile retail stores.
To use a promotion code online for a purchase, enter it during the checkout process. Once you have added the appropriate items to your online shopping cart and you are ready to complete your order, click the pink Check Out button on the cart review page. You need to either log in with your T-Mobile account or complete the required information for shipping. On the following page, you are prompted to enter billing information. Enter the desired promotion code in the appropriate field, which applies it to your order and gives you a new total price.