With the smartphone type (Windows Mobile, Symbian, Android, Palm OS, iPhone) which is a mini-computer anyway, you can treat it as such and use wipe disk utility to clean your phone. With knowlege about the phone OS, I think one can erase the private data for good.

Regular phone with a built-in flash memory and a SIM card is much harder to scrub. But scrubbing with bleach is not a bad idea

Nathan

Well every phone has a way to do a factory reset. Do that a few times, that should take care of it.

Other way is to reload the OS a few times as well.

But, if you are that worried about people getting data off of the phone, the safest way and most secure way is to destroy the phone and SIM.

I'm talking about turning it on and putting it into a bucket of bleach mixed with water for a day or two.

That'll destroy it for good.

I search in vain so far on Internet for definitive answer to my question: How do you erase your mobile phone data (numbers, messages, etc....) permanently so your data cannot be recovered with utilities such as Mobile Phone SMS Recovery.

There are manufacturer instructions from Wireless Recyling that suppose to erase data in your mobile phone, but it doesn't explicit state that the data are erased permanently or not.

Without a definitive answer to this question, the only thing that one can be sure to safeguard the info is to completely destroy the SIM and the phone itself.

Nathan