Black screen while using

[Wildwegge]

I have an iPhone 7. About once every 10-14 days while using Spotify, the whole phone screen will go black and unresponsive (except being able to change the volume). The home and lock buttons don't work, so I cannot safe restart the phone. The only thing that helps me get out of the black and unresponsive screen is if someone sends me a text message, which I can click on to exit Spotify. Please help!