I purchased a refurbished S9 from Amazon Marketplace. I have discovered that its an American import with a CSC of XAA so it wont get the 2020 Security Updates or Android 10. Trying to update from phone or from PC via SmartSwitch both just report that phone is up to date. I was told that downloading a UK firmware with CSC of BTU was the way to go but when I search for firmware for my exact model which is SM-G960U I don't get the option for BTU. That option only seems available for model SM-G960F. Can I use the latest BTU firmware for model F on my model SM-G960U without a problem and if not how can I get my phone updated here in UK? Many thanks for any advice on this.