I got the 1000 min promo plan with internet. Ordered it online and when the phone came the internet didnt work so I went to the local tmobile store. The person from the store called support and had internet added rightaway. If you want to add it yourself on my.tmobile.com then you'll have to downgrade to the 300 min plan.

My opinion, it helps to have a tmobile employee make the call and it might help if you are still within the 14 day return policy. They know at that point they can either give you the internet option or loose you as a customer entirely.