ITunes does not recognise iphone 6?

I have an new iPhone 6 and after setting it up, I realised something. When I plug the iphone into my mac computer using a lighting cable, iTunes does not recognise the device. No prompt message on anything, just no device on iTunes. Yet if I plug my iphone 5 in, it recognises it fine. The phone charges when i plug it into the mac so the computer recognises the iphone 6, just not itunes.

I have the latest itunes and latest iphone software, but i'm not sure what I need to do in order to try and fix this. Has anybody got any ideas or trouble shooting i could do to fix it? I need my music

Will I need my own appleID, I'm using the same as my brother and his works fine when he uses his itunes on his laptop (he is in university far away so I can't test it on his laptop until a couple of weeks).

Extreme amount of data usage: 1000 MB used in 8 minutes?

For my iPhone I have a plan of 2000MB a month and I try to keep the usage down by only turning on 4G when I really need it and only one app at a time (and I'm usually connected to Wi-Fi). But in the last two weeks I have somehow used 11,000 MB of data. (It adds another 1000MB each time I go over.) But I have gotten notifications that I have already used another 1000MB within 10 minutes of eachother when i have NOT been using my data. I'm definetly going to change my plan now but I just want to know if this is my fault of a flaw from AT&T? Because I really don't want to pay an extra $135 for the extra data charges