If your remote won't lock/unlock from a distance but still works when held against the door handle, it's a low fob battery. Most fobs use a CR2032 coin cell — under $3 at any drugstore.
Pry the fob open at the seam with a small flat screwdriver, swap the coin cell (note polarity), snap it back together. Most modern fobs do not require re-programming after a battery change.
If the fob is dead and you're locked out completely, call us. Lockout service is our standard $249 / hour rate, 1-hour minimum, $224 first hour online.