You were correct, Virgin is the setting you want. In a poor reception area battery drain due to repetitive network searching is significant - but under 1% per minute. What is most likely the case here is - when you took the battery out to change the sim card the battery monitor chip reset. It probably overestimated both the change level and capacity when you put the battery back in. So you were seeing an estimation of 39% when the true charge was something more like 5%. After a couple of full discharge-recharge cycles it should be back to normal. It could also be a symptom of a failed / EOL battery - do you still get a decent amount of screen on time?
Ive had issues like this on my android phones before and my partner had the same issue very recently clearing the phones cache normaly help resolve it but then could be the battery if dead but try this out this is what i did on my old samsung s3 when it used to happen
Turn off phone Remove the battery and reinsert. Hold down the Home and Volume Up keys Press and hold the Power button while still holding the other keys. As soon as you see the Samsung logo, release all keys/buttons. Press on the Volume Down to scroll down to Wipe Cache Partition. Press the Power button to select it. Press the Volume down button to highlight "Yes" and press the Power Button to select it. Wait for a few minutes for the phone to clear the data. Then press the Power button to select reboot system now. Wait for your phone to reboot.
@mrgrey1 Is your phone running hotter than it used to on GG? What is your signal strength like (dBm)? Does changing the network mode to 3g/2g or even just 2g (but best to turn mobile data off on 2g) improve the battery life?
I only mentioned end of life due to the likely age of the battery really. Did you fully recharge your phone from 0 to 100% in one go?
To add to the helpful information that @Magic_M and @sharkman3d have given, we would also normally ask for you to make sure that the following things have been turned off:
These facilities can also cause problems with battery draining, this is because there always searching for a connection.
There is a code that you can enter which will tell you how the battery life is on your phone, this is an android short code, however it doesn’t work on all phones. Try dialling in on the phone key *#*#4636#*#* this should take you to a test menu from there select battery information. This should load up the battery menu and about half way down it will say battery life status. This information is available on line as well, please be aware not all android phones will accept this code.
We also had a memo sent out to us confirming that there was an issue with the Facebook servers causing a huge power drain on android mobile devices on the 10th and 11th of January, if you have opened your news article directly from Facebook, this could be another factor. if you have Facebook have state the following to resolve this:
Closing the Facebook and Facebook Messenger applications and restarting them should see battery performance return to normal.
To close both of these applications, push the task button and find the Facebook application and swipe left or right to close the application, repeat this for the Facebook Messenger application. Alternatively, use the CLEAR ALL option to close all running applications.