Hello, when I use iBooks 4 on my iPhone 6 while I am out of home (cellular data), it eats up permanently cellular data in the System Services section under "iTunes Accounts". And I mean, a lot of data, 10 MB in 2 or 3 minutes, until I kill iBooks. Cellular data for iBooks is off and it is only shown in the System Services, but I can perfectly repeat the process: start iBooks and reading -> after 1 minute there are 5 MB more gone from my data plan... Yesterday I resetted the phone and set up as new device: No solution...! Any help someone?