Yes this a common problem, some people like you genuinely try to avoid overloading official support, some think this could be official support, so sadly your trying to relieve them initially from the problem isn’t really helpful to you and, irrespective of FP’s workload isn’t helping them.
When i see people post a problem that isn’t resolved on this forum with two or three weeks, or sooner, i advise them to open a ticket.
Sure it puts work at the door of FP, but they are not going to know the consequences of their business jf many customers don’t complain promptly. And no doubt as you have found, delays in official complaints can lead to querying your integrity.
Let’s hope you can sent the phone back and get some compensation once they see the problem in their hands.
All the best