How to disable all predictive text on blackberry pearl

It sounds like you have followed the correct procedure, but make sure it is 'auto-correct'.

https://www.google.com/search?q=Doro+5680+turn+off+predictive+text

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To turn OFF predictive text mode, press and hold the # key.

To turn ON predictive text mode, press and hold the # key. The icon at top-left (next to abc, Abc, or ABC) moves right.

Alternatively
Enable or disable predictive text
From the home screen press the Menu button. Move the cursor to Message and press the OK button.

Hi, You can unlock a Blackberry Pearl 8100 safer and easier using unlock code. You can get the unlock code for a Blackberry Pearl 8100 from www.superunlockcodes.com/blackberry-pearl-8100/rs12wp9/ at affordable cost.
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UNLOCKING STEPS FOR BLACKBERRY PEARL 8100
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1 - Switch ON your Blackberry Pearl 8100 with your current network/service provider's SIM card,
2 - Go to Options Menu => Advanced Options,
3 - In the SIM Card menu, hold down the Shift (right of the zero, cap) press meppd, (NOTE: You may not see any text appear on the screen while typing meppd)
4 - You'll see the unlocking level screen there you hold the ALT key (left side below @) type mepp2, (NOTE: You may not see any text appear on the screen while typing mepp2)
5 - Enter the unlock code.

what exactly is the text problem...here are some general solution for text prediction

1. options > auto text > edit > clear the with field ( this solution is used for instance if you keep type hr and it comes out as hour and you want to change that)
2. options >auto text > new > enter word ( used to add a new word to auto text )
   
3. options > SMS > disable auto text : YES ( used to disable auto text or test prediction )
   

Go to message writing mode and press # button for 3 seconds.

1. Go to the main applications view on the Pearl.
2. Choose Options (it's the little crescent wrench icon) and select it.
3. Scroll down to Language and click the trackball.
4. Under "Input Language" you want to either select your language with Multitap (to enable Multitap) or without (which puts you into SureType mode).
5. Now just click the menu button and select Save and you're back to normal.

Although BlackBerry is a fairly reputable company, the complaints that you describe above are quite common, and most without fixes.
If you want a BlackBerry, consider the 8220 BlackBerry Flip. Better predictive text engine and none of the complaints you mentioned above. I think those are available well within your price range if you're willing to do a new two year agreement.

try holding the key on the left that looks like an arrow. While holding this key hit LGLG. Then change the warning portion to debugging. hit the menu key to erase the log.

can't change from predicted to normal texting

replace your phone