Post Disclaimer: This post is based solely upon my own personal experience - and BRN has absolutely nothing to do with it.
Purchasing or using a VPN app from Google Store just isn't the way to go - in terms of reliability, problem resolution, technical support, and above all else - security (especially against IpV6 leaks).
Disable IpV6 on your Android if you are able to on the device. It is best to ask the provider before purchase if their VPN client has native support for this on Android.
Ask if anti-DNS Hijacking has been implemented.
Something to consider, but just be aware it was funded by IVPN:
VPN Testing
The test results in the above report "jive" with reputable academic researcher findings.
However, technically the downside is that one cannot interpret a PC-based VPN test to provide equivalent performance and protection on an Android device.
I would ask the vendor to produce some kind of meaningful data\report. It isn't an unreasonable request. Then you can judge for yourself.
Technically optimal security, great customer service, solid technical support and transparency:
007 stuff...
Both can be used on Android. If it does not work out for your mobile device, then IVPN offers a 7 day refund (there is no contract anyway) and Mullvad a 30 day refund policy.
Both vendors have device-specific technical advice. Ask about it before deciding to subscribe..