Apple has confirmed that the iPad and iPhone micro-SIM cards are not interchangeable.
When asked by owners of the devices if the micro-SIMs would be interchangeable, the company replied with a simple "No," before stating: "Your iPad micro-SIM card will not work with your iPhone."
According to Apple, both it'gadgets use micro-SIMs but the iPad's SIM does not support voice features.
Instead, it's designed only for flexible data services, such as pay-as-you-go data transfer. The micro-SIM for the iPhone focuses on voice and other features including SMS.
The news comes as a disappointment to customers, who had hoped to use leftover data allowance from one gadget on the other.
UK network services provider O2 assured its customers that it would soon come up with a convertible SIM card that would work in both devices.
The news comes after Apple and AT&T's websites were overwhelmed by demand for the iPhone 4, preventing customers from placing pre-orders.