It depends on what is causing your battery problems. If it's the charger itself, you may want to check the connection between the charger and the phone, or replace the charger all together. Another cause of short battery life is an improperly functioning battery. Batteries, especially on older phones, weaken over time. Replacing the battery may get you the extended use you want.
You may simply be in an area with poor reception. Sometimes calls can still go through, but the poor reception obstructs your ability to hear the person on the other line. If you're sure you are in an area of good reception, the speaker in your phone may be damaged. If so, you'll want to replace the speaker.