That's sad. You must know the brand and model of your batteries and charger.
Never assume the salesperson knows more than yourself when buying batteries and chargers. For all you know they could have sold you a protected ICR battery instead of a high-drain safe-chemistry IMR battery. Many vape shops are getting into the market only for a quick buck and don't have the background to know which batteries work best in what applications.
Do yourself a favor and take a good look at your batteries and report back what markings are on the battery so that we can identify it.
Battery Basics for Mods: IMR or Protected ICR?