When I type a message and the letter "A" is required, the letter a does not print, it comes up with * instead replacing the a. Is that a sticky key issue or is something else locked on that i am not aware of. I am NOT tecky as you can probably tell. I am an old guy with a phone that i should not have.
When you type (Q10 I think) don't you touch the Alt when going to the A? If so this means maybe the Alt has sticky problem. Or use some soft air to clean keyboard.
If the result is: * 4 then your alt arrow on the bottom left is in the locked position.
If the result is: * s then make sure you are not hitting the alt key first as it is just below the "a". Can happen if you have large fingers.
If you are for sure 100% positive you are not hitting alt first and it isn't in the locked position, then only other thing is hardware issue. Call your carrier.