What type of contract did you have in 2011?
What type of contract did you have in 2012?
What type of contract did you have in 2013?
What type of contract did you have in 2014?
What type of contract did you have in 2015?
What type of smartphone did you use (most) in 2011?
What type of smartphone did you use (most) in 2012?
What type of smartphone did you use (most) in 2013?
What type of smartphone did you use (most) in 2014?
What type of smartphone did you use (most) in 2015?
How much did you spend on your phone during 2011?
How much did you spend on your phone during 2012?
How much did you spend on your phone during 2013?
How much did you spend on your phone during 2014?