OK, I see. But if I understand what you said correctly, your issue is that you removed the rechargeable batteries to verify that the batteries are full (and you verified so), then simply tried to put them back into the hearing aids, but now they don’t work anymore even though they work before, right? So the seller’s statement is irrelevant, because the problem is not even about charging up the batteries with the correct charger, right?
May I ask why you felt the need to remove the batteries to verify that they are full? Can’t you verify on whatever smartphone app the Bernafon came with for the battery level there?
And how did you verify that the batteries are full without the app? Did you put a voltmeter on the batteries themselves? What voltage did you get from them? How did you determine that the voltage you read indicate a full charge?
Is it possible that while the batteries are out and being measured with a voltmeter that the probes inadvertently shorted the batteries?