Problems with sound and sound volume in Zoom

I am using an iPhone 6: (I know: some of you think I'm in the dark ages, lol.) When I use Zoom, the sound quality changes; it sounds like I'm hearing things over the phone. If I use the option to activate the speaker, it gets a bit louder, but I still need to stay really close to the phone to hear. The volume is set to 100 per cent. I don't think I had this problem when I first started using Zoom. Things are generally fine when I do other sound related things like reading books from BARD. t

Any help would be most appreciated.