A:AnswerI suggest you reach out to your carrier whether they support WiFi calling for this phone or any phone and Best Buy's webpage for OVERVIEW and SPECIFICATIONS or Phonearena.com website does not include the information about WiFi calling for this phone.
A:Answerdepending on your location within the United States depends on whether this phone will meet your expectations; I recommend you visit the US Cellular website and review their coverage map and make your decision based on coverage. https://www.uscellular.com/coverage-map
A:AnswerNO! you cannot add more internal memory to a smartphone, any smartphone. The 6GB memory of this device is permanent, if you want more memory then look for the S20 variants (S20, S20+, S20 Ultra....)