Hi @Valis Inc. 

Have you tried switching to a different carrier, if available or test the sim card on a different phone? 

Unfotunately, I didn’t have another phone to swap the sim card out.  I wasn’t aware that I could choose different carriers when traveling.  I guess one would do that in the “choose network” settings? 

Yes, you should be able to switch from Automatic to Manual network in the network settings, and then select a different network carrier to connect your phone to. 

If the problem persisted across different US networks what else might cause crackling/dropped sound on voice?

Are you using VoLTE when in the US?

https://www.koodomobile.com/en/help/3gshutdownUS

I’m not sure where VoLTE is accessed specifically but the preferred network type was set to 4G/3G/2G/Auto.  I noticed it was currently connected to 3G (I’m in the basement).  I went upstairs and got connected as LTE and came back down and it’s now on LTE.  It may have been connected as 3G in the US.  The data seemed to work fine.  Note: I am currently having a hotspot not sharing internet problem.  I did a separate thread on that issue:   No internet available through hotspot | Koodo Community (koodomobile.com)

Thank very much for your help!