Issue with my charger for my phone: Motorola MOTO W755

Out of nowhere my charger for my Motorola W755 stopped working. I had an old motorola charger that fits my phone, but when I plug it in it says "unauthorized charger". I went to the Verizon store and they gave me another Motorola charger. It wasn't the same one I had previously had but I figured they knew what they were doing. I tried to charge my phone with the new charger and still got that same message. I guess my question is, is there anything I can do to make one of these chargers work? For instance, do I need to maybe change anything on my phone for a new charger to work? Thanks a lot for any help