Unfortunately troubleshooting the problem is just that, it could be the hearing aids, it could be the phone. I would start by clearing out your phone, all open apps, deleting the hearing aids from the phone and then restarting the phone and pairing the hearing aid to the phone again. If it happens more, I would double check the phone is within a few feet of your hearing aids. If all of this doesn't help then I would send in the hearing aids for repair and if it continues then I would replace the phone.
Good Luck
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