Worst Customer Service from Infinity Battery in Phoenix

We bought a brand new battery at the Infinity Battery - Lenham Phoenix. This battery is still under warranty, yet my car is struggling to start and when I checked the battery life the amps was supposed to be 400amps, the battery I have only has 178 amps. We took the battery back to the shop we purchased and the counter hand accused us of bringing a **** slip showing the amps. He said we had gone to a **** battery dealer and got a reading. He then asked us to come back as the owner was not there for a refund and gave us an Infinity Battery sticker - said we must call the *** number if we want the battery refunded. Upon calling the number for Infinity number it goes into voice mail. If this is not ****py service, and being given the ****** run around, then what is?