Want to change rate plan for existing phone number, the special rate plan is advertised but not appearing in checkout.

Hello,

I am looking at ordering a new phone and changing my rate plan as an existing customer.  The rate plan change is necessary to order a new phone with a tab plus.  I have a special promotion available that is $65/month for 40GB data, but the first 15 months are $50/month.  This rate plan allows me to get a tab plus for a new phone.  However, when I go to check out I do not see the promotion, and instead it shows only the $65/month plan.  There is no mention of the $15/month discount for the first 15 months. 

I am hesitant to make the switch without confirmation of the discount as that is what makes the phone purchase worth it for me.  Is there any way to get confirmation of this special rate plan before confirming the purchase?

Thanks for any help!