Following are the Disadvantages of VOLTE. These are based upon users reviews.
1: First at if all its not been available in all mobile handsets. VOLTE should be available in all handsets to obtain all features of VOLTE
2: You cannot get HD call quality if you are calling from VOLTE to other networks. HD call quality is only possible if you are calling between 2 VOLTE supported handsets.
3: Now lets talk about internet connection if you didn't nt have internet access nor have 4G roaming in the area then you will not be able to call and you cannot use internet services.
4: VOLTE service are not available everywhere so it will be challenging for you to get complete roaming services because it required some specific network. And also it requires higher amounts to get VOLTE services because VOLTE enabled handsets are costly.
But with the help of continuously improvements and research VOLTE services will be available in all areas and price issue will be vanished with the passage of time.