For those who want to use dual SIM cards on your iPhone 4, here is the solution you need. The solution includes an adapter the will hold two standard-sized SIM cards, meaning you don’t need to cut your SIM card, and an case that has space for the two SIM cards.
This dual SIM card, however, doesn’t support dual standby mode. Instead, users can switch between cards. This iPhone 4 dual SIM solution is priced at $28.99.