My mum has recently brought the bt3570 phones and while setting it up we can not work out if we are able to lock the keypad when the phone is not in use. We have animals and they tend to like to press things when sitting on it.
Is there a way to lock the keypad when the phone isn't being used?
Doesn't look like it. That facility is usually implemented on BT phones by pressing & holding the hash (#) key. On this model that seems to toggle text case. If the facility is important she would need to try to return them & exchange for something like the BT4600.
Manuals for phones are usually available online or images from retailers should show the keypad. It will either say "Lock" or have an image of a padlock.