If you had the relevant keys? You wouldn't even need a blank card. You could just make a software emulator and force the smartphone modem to use it. The obviou

If you had the relevant keys? You wouldn't even need a blank card. You could just make a software emulator and force the smartphone modem to use it. The obvious issue being: it's pretty hard to acquire raw key material. Most vendors refuse to sell it, and the workarounds are messy.