I am not a professional smartphone tech. nor I.T. trained. You may wish to follow along with my own layperson thoughts that I am happy to share here after my internet research. Your own thinking & conclusions are also necessary. Hopefully I can save you some time by sending some of your thoughts in helpful directions & towards useful questions.

Some believe that WiFi (VoIP) calling can be one of the solutions for “crystal-clear calls”; for those looking for excellent sound quality.

WiFi calling is generally VoIP calling. There have been improvements in call quality when using VoIP systems (I read that many past challenges have been addressed). I note additional things to do or consider for better chances of a “reliable & uninterrupted [WiFi] calling experience” (sounds useful). It seems like most of the following might help when encountering imperfect conditions. Let’s review some factors that may improve audio clarity; “speed of data packet transfer”, & towards a lack of interruptions and/or delays  On calls important to us (important for whatever reason), we don’t want interruptions or miscommunications caused by bad calling conditions.

Suggestions, include:

1. pricey equipment doesn’t always mean better (e.g. a better headset); as usual, current users’ reviews can be informative;

2. one vote was for noise-canceling headphones (advice: to look for ones that deliver sound evenly to both ears);

3. “USB corded headsets typically provide a more stable sound quality than Bluetooth or wireless headsets.”; &

4. lots of comments about the importance of a quality router, though when traveling we might not have control over that factor.

1. Seek to connect to a “reliable & high-speed internet network” (ask about that when you can & in case you have choices).

2. Pursue better signal strength, a better connection while calling by “moving closer to the router or access point”.

3. Move other devices further away from the router or access point; doing this might minimize interference from them.

4. Don’t download large files or stream high-definition videos at the same time (as the phone call) & “close any unnecessary applications or programs running in the background on your device”. Overloading the internet connection’s bandwidth can decrease your call’s quality; instead, try to keep more bandwidth available for the call. When VoIP calling, “adequate bandwidth is vital”.

5. Hmmm: consider assigning a static IP address to the device you use for WiFi calling (something to check into).

I seem to find *free pages/tests on the internet to perform all of:  a Speed test (re: the speed of your internet connection); a Ping test (re: the latency of your internet connection); a Jitter test (re: the variation in latency); & a Packet Loss test (re: the amount of voice data lost during transmission), usually with further info. there what the test results may be communicating.

And there is also VoIP monitoring software (some of it offered *free) that measures a variety of factors.

(*As always with free stuff on the internet that is going to interact with my device, I try to assess if it’s from a reliable name/website. Use caution.)

Other Troubleshooting to Consider:  You might try checking on firewalls (if you have same), that they are not “blocking the flow of traffic.” (I would probably consult a phone tech for that suggestion).