Well, for starters, a little bit more information would be helpful.
What type of phone?
Is the battery rated as a suitable replacement for your phone?
Does it charge completely? Keep in mind it may not charge correctly from a PC if using USB. Depends on the PC.
Also, new batteries usually need several "FULL" chargings before they begin to settle down. Keeping it plugged in for an hour or so after a full charge is good.
Check the specs on the battery itself, and see if your wall charger has the "umph" to properly charge it.
Anyhow, more info would lead to a better solution.