Changing iPhone paper size in printer options

I was unable to change iPhones setting from 4x6 back to letter although I was able to print letter size from my laptop. No options for other paper sizes appeared on my iPhone. Solved the problem FINALLY by sitting in front of my printer, pulled out the paper tray, pushed it back in and then the screen on the printer prompted for change format from 4x6. Changed to letter and now the iPhone printer options shows 4x6! Success!!