activating t-mobile apple sim 5G 150 days deal iPad 4 mini

I am trying find out if other people are having trouble activating T-mobile on their iPad mini 4 for the 5G for 150 days for $10 offer. When I try to complete the transaction through the activate cell service on the iPad mini I am told to call customer service. Customer service tells me they cannot activate me through my CSN or apple SIM card number. They stated the format of the apple sim card is incompatible with their system. The physical store told me to do it on-line. I do not have phone service with T-mobile and do not want to get a T-mobile sim card which defeats the purpose of the apple sim card.