Which one is correct?

A. The letter "O" was CHANGED TO letter "X".
B. The letter "O" was CHANGED INTO letter "X".

Thank you in advance!

Question

Which one is correct?

A. The letter "O" was CHANGED TO letter "X".
B. The letter "O" was CHANGED INTO letter "X".

Thank you in advance!

Answer

Changed TO  :    O was removed and replaced by X
Changed INTO  :   O was somehow transformed into an X.

For most cases you probably need the first one.