I understand what you mean. My phone's speaker is a bit low as well. Now the alternative for me is if I listen to music on my phone I use stereo headphones. When i am at work, I have a portable Mobile speakers that work well for me.
I hope everything else is great with your phone.
Thanks for posting and welcome to the Community
I just played around with my Plantronics Bluetooth headset and the volume was fairly good, though it definitely wasn't ear shattering. I suppose in a crowded or noisy situation it might seem a little quiet, but some of that may be on the headphone as well. If you were using headphones before, have you tried a different pair?