Hi,
some question to understand...
- Have you already tried a second pair of headphone? Just to understand if the problem are the headphone or the iPhone...
Look at this article for further information
--- > https://support.apple.com/en-gb/HT203026
- Have you checked if the bluetooth signal is experimenting some interference?
Look at this article for further information
--- > https://support.apple.com/en-gb/HT201542
- The headphones might lose their connection more often with streaming audio than with content that is stored on the device.
Try the test that is suggested in this article (Improve your Bluetooth connection)
--- > https://support.apple.com/en-gb/HT209369
- Have you already tried to unpair/pair the headphones?
Look at this article for further information
--- > https://support.apple.com/en-gb/HT209369
If your headphones continue to disconnect, contact Apple Support.
Let me know if you solve it...