Working in a retail store, 85% of the time requires phone calls or answers. I used to work in a grocery store as a cake decorator, most times I did not have to answer the phone for orders but there are times where I had to take the calls. Game stop is a very small store with only 1 or 2 employees at a time rarely I see more than 2 so they need you to answer phones.
It is a 2 way tho, He/she should have asked you if you can take phone calls etc. You on the other hand even tho you said it was not hinderance but could have said do I require to take phone calls etc, if so I may have some issue with that.