Unfortunately the person that sold you the phone is clearly clueless. That charging scheme is ridiculous! Ignore that advice. Also, anyone with a clue about Android knows that task killers have not been useful since version 2.1 days. Remove it immediately as it is probably costing you power. Next install Juice Defender with just default settings and you should see a large improvement in battery life. There may actually be a problem with the battery for many of us, but I would wait for some of the experienced users to come up with more information before going in about it.