You can increase speaker, Headset/earpiece, Headset speaker volumes with MTK engineering mode app
Requirements
1. Engineering mode app download below
Steps
1. Open MTK engineering mode app and navigate to Hardware testing tab
2. Select audio and choose which you want to increase either speaker or headphone/earpiece volume.
If you dont have issue with the volume of your earpiece [little speaker used to listen when making or receiving calls], i'll advice you leave the normal mode alone
3. For headset volume ensure not to go too close to the max volume so as not to get a loud dirty sound just add up a little
The 150 max vol still gives a little dirty noise like the speaker is too loud so ensure not to go above 150 or upto 150 and also leave the value alone it should be at default