How to Enter Unlock Codes on Treo 600, 650 and 680 Cell Phones
Remove Treo battery,
Insert incorrect SIM card (Any simcard that the phone does not accept)
Power on Treo-650, 'Sim not allowed' is displayed, click OK
Go to the dial pad, and use the stylus to enter MEP code . You must enter the code in the following fashion:
*#*#(MEP-CODE)# then press dial (Where (MEP-CODE) is to be replaced by the ACTUAL code supplied by the unlocking software)
For example if the software supplied 12345678 as your MEP code for your phone , you must enter the code as follows:

*#*#12345678# , then press dial

Again the above numeric code is for illustration purposes, please enter the MEP code as supplied by us. Phone will reset and display sim lock removed

Troubleshooting:

Error Message: "The SIM Lock has NOT been removed from this phone"

Solution 1: Please make sure you are entering the correct code and enter it using this method *#*#CODE# dial

Solution 2: If the phone says that the SIM lock has not been removed, ensure that the phone radio (wireless mode) is on.

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TREO 750 Unlock Code Entry Instructions

How to Enter Unlock Codes on the Treo 750
1)Insert NON-Cingular Sim card in the phone

2)The phone will ask for the Unlock Code

3)Please use your Stylus and choose the little Keyboard Icon on the bottom middle of the screen

4)Enter the code on the digital keyboard that appears on the screen

5)Then click again on the little keyboard Icon at the bottom middle

6) Click OK

7)Your phone is now unlocked

If you see a message that says "Timeout" just leave the phone on with that screen and the message will dissapear after a while and prompt you for the unlock code again