I bought these headphones recently. But with my Huwaei p20 pro. The sound is very very weak. With another phone, no problem. Do you have any idea what the problem is?
I don't know what your other phone is, but if it's a Samsung, there is a volume sync option between the headphone volume and the phone volume.
The headphones have their own volume (managed with the buttons on the headphones) and so does the phone. So you'll have to look for a volume sync option in the phone between the output and the phone.
It's also worth noting that the last update to the jabra 75t reduced the maximum volume of the headphones but I don't think that's the problem.