I'd be more than happy to assist you. By design it's going to be harder to hear someone on speaker phone. But because speaker volume being low is so subjective without hearing for myself it's hard to say if your phone is defective or not.
Do note however speakerphones on mobile phones generally are pretty poor. You'd have to keep the phone still very close by when speaking with little to no background noise. That said I can offer you a suggestion/alternative. Have you considered getting a bluetooth headset or bluetooth speaker/speakerphone to augment your mobile device? That's an option and I'm happy to suggest some models if you'd like.
I'm sorry you don't feel as though I know what I'm talking about. My answer can only be as good as the information you provide. Hence I asked for clarification and stated "speaker volume being low" is subjective. The issue you described in your last comment is more detailed and does indicate a defective phone.
I'm going to go ahead and opt out of this question since it doesn't sound like you're happy with my service. Another expert will jump in. Thank you.
Hi there Leonard
Is this issue only occurring with one person or anyone that you call and then use the speaker function?