I want to set up 2 different plans with separate equipment at 2 apartments within the same complex

I have already ordered one plan for one apartment, and now when I try to put in the address for the second apartment it says there is already a plan at the address. I have confirmed the 'other plan' is my own, and have specified the separate apartment numbers on each of the plans, but nothing seems to work. It would not be possible for the two units to share wifi. In short, how could I get around the system thinking that the addresses are the same?