Why do I lose virtually everything when I a) upgrade or b) download updates?

[iMore Question]

I've noticed that whenever I've upgraded iPhones or downloaded the latest updates I lose virtually everything. Example; upgraded last year from 5 to a 6. Lost 150 songs in the process. Tried Apple's helpdesk. The answer I got wasn't even an answer! Also, tried Vodaphones webchat as that is who I got the upgrade through to no avail.
Today I updated to IOS10 and lost all but 26 songs. For some reason I can't download my songs from my laptop to this phone. I had no problems when I upgraded from a 4 to a 5.
Getting fed up of iPhones. Any suggestion?

 

[Just_Me_D]

To be honest, I don't know. I've yet to lose anything from merely updating to the latest iOS version....EVER. By the way, how did you update? Via iCloud or via iTunes?