I've never had any complaints about the quality of Bluetooth calls with my previous Accords. However, my 2018 drops calls all the time, and it's irritating. My previous Accords didn't drop calls. I'm using the same phone as before.
I'm using and old Android 4.1.2. However as I indicated, neither my 2010 Accord, 2014 Accord, nor my 2011 Ridgeline dropped calls using the same phone. My 2018 Accord drops calls frequently, almost every time I use it.
I still have my 2011 Ridgeline and have no issues with dropped calls. So, based on past experiences I don't think it's a problem with the cell towers or phone hardware/software. However, it is possible that the 2018 Accord software or hardware may not work well with my version of Android. BTW, every other Bluetooth feature works fine (contacts, favorites, call logs, text, etc.), and the quality of the calls is good.
What's strange is I don't recall anyone else mentioning the problem, even on the other Accord message boards. It's very irritating but, I'm not willing to buy a new phone because I'd be highly upset about wasting money if the 2018 Accord is the problem.
When you say " My 2018 Accord drops calls frequently...every other Bluetooth feature works fine (contacts, favorites, call logs, text, etc.), and the quality of the calls is good.", why are you circling in on bluetooth as the problem?
Are you saying if you are talking on speakerphone (not bluetooth), you have no problems?
You dont mention make/model or how old your phone is but have you had someone with a newer phone experience same thing in your vehicle?
Bad guess (since it is not a wide spread issue) is maybe your phone has bluetooth 1.2 and you Honda 2018 headunit is backwards compatible since you can make some calls and other features work, that maybe the difference in technology is that the older phone and newer head unit lose comm negotiations when there is a lot of traffic on bluetooth (aka talking). When it looses sync, it just aborts connection.