Your comment makes no sense, since reusing those frequencies for more efficient newer technologies (4G) will improve their network.
The reason that 2G has better signal quality than 3G in your area is that the 3G signal is overloaded. Since 3G phones will prioritize 3G signals over 2G signals (since they are more efficient and capable of more bandwidth) and most people have 3G phones, most phones are on 3G signals.
AT&T are in a bind right now (as are most other cell providers). More people are trying to use more data over wireless all the time, which means that their cell networks are getting overcrowded and way oversold. They need to add more capacity, but that requires either more RF bandwidth (necessitating new phones/devices to use the new frequencies) or they need to replace their current services with more efficient protocols that are more spectral efficient (moving to LTE). This is part of the latter. By reusing the bandwidth that is currently in use for 2G as 4G (or shift 2G -> 3G, 3G -> 4G), they can add more capacity to their network, thus improving the network quality for everyone (except those still using 2G only devices).