You can order a SIM card from T-Mobile on line. They are sometimes free or may cost $1. They come with $2 of credit on them. You use the credit on the card to call T-Mobile can complete the activation and pay your prepaid service. The SIM comes with activation instructions. Basically you go to www.T-Mobile.com/PrepaidActivation. You have to enter an activation code, SIM SN, phone SN/IMEI, etc. After this you will get the option to pick your plan. It is only at this time that you will finally see the $30 plan listed. It is tricky to find so you"ll have to scroll around to find it. You can also call an agent at 1 877 778 2107. T-Mobile doesn't advertise the $30 plan so you have to be aware of it to get it.
Good luck!