Why do I have problems charging a Samsung Galaxy S5?

[AC Question]

When I try to charge my Galaxy S5, I hear beeps which seem to indicate that there are power interruptions while charging the phone. I took it to my cell phone service provider and was told that I should only use OEM Samsung batteries, cords and adapters. Is this true or is there a problem with my phone's charging port? Also, is there a particular external battery that would suit the S5 better than others?
Thanks