Totally format your Nokia 3650 and remove all installed applications, etc

First Format your MMC: Menu > Extras > Memory > Options > Format mem. card > Yes.

Note: It is very important to format your MMC before you format your phone!
Then format your phone by typing *#7370# on main Phone screen.
Phone will ask: "Restore all original phone settings? Phone will restart." Press 'Yes' and enter your Lock code (default is 12345).

Tip: Formatting takes several minutes so you'd better connect your Nokia 3650
to a charger to ensure that your battery doesn't get empty in the middle of formatting.
Note: All your created acces points and mailboxes will be lost so take a note of them. And all application settings will be reset.

E.g. In Camera, image quality is set back to normal and memory in use is set back to phone memory. And also in Messages,
memory in use is set back to phone memory, etc. Also backup your contacts with PC Suite or a program like Contacts Manager.