We have an old at&t Merlin phone system and that could be the cause of volume issue but not sure. If you buy this box and volume is too low for cell phones, I recommend buying the IBOOST to solve this problem.
Slow your roll—there’s a lot more to hold music than just genre. A phone line isn’t a state of the art speaker system; its primary function is to make sure the call is connected. Volume changes, frequency, and distortion are all elements to consider when choosing hold music.

Easy On Hold Founder Tim Brown says that the new scheduling mechanism is what makes the Easy On Hold streaming message unique. "The traditional four-minute on-hold loop, where several paragraphs are edited over one piece of music, is an outdated approach," he says. "Our service puts together a library of individual spots that can be told when to play and how often. You can schedule start and stop dates, too, so old content is never heard."
Corporate cost-cutting and new technology have resulted in the advent of automated systems that can make the on-hold experience even more frustrating. It can feel near-impossible to get a human on the phone these days, which a national survey conducted by Consumer Reports found to be Americans' second-greatest annoyance, after hidden fees but beating out inaccurate weather reports and dog poop. Green observes that often people call as a last resort, because something on the website wasn't clear, perhaps, and they really need an answer quickly. So callers are captive listeners, a state often associated with the gridlock of waiting, whether in line at a Starbucks, in a dentist's chair, or in the proverbial elevator making its slow way up.