You can definitely replace a Vodafone SIM card with an Orange network SIM card on your Sony Ericsson K800i. But make sure that the cell phone is unlocked from network restriction in prior. If not, you need to unlock the cell phone before swapping SIM cards. You can unlock a Sony Ericsson K800i safer and easier using unlock code. You can get the accurate unlock code for a Sony Ericsson K800i from SimpleUnlocking.com at affordable cost with an easy unlocking guide. Good luck.