It's pretty simple - their Customer Service! Here's the story: Starts in November - had an iPhone 5 and iPad 3 (32gb cellular AT&T). Purchased an iPad mini (64gb cellular AT&T) around Thanksgiving. Switched my data plan from the 3 to the mini thinking I was probably gonna get rid of the 3 - cost $30. Few days later I'm at a mall with an AT&T kiosk and decide to check out the data sharing plan. Guy signs me up for my iPhone, mini, and other cell phone line (only had this in order to upgrade 4S iPhone to 5) for limited minutes and text. He refunds the $30 I just paid for mini plan and waives activation fee of $36. Week later decide to keep iPad 3 and set up $14.99 cell plan for it AND then decide to add it to my current AT&T monthly bill so everything is on one bill. They charge me $36 activation fee to do this. Really? First bill comes in early December and it still has the $30 guy at kiosk promised to refund plus the activation fee he promised to waive. I call Customer Service and they immediately credit both activation fees and the $30 - took total of $102 off my bill. Perfect! I decide to go ahead and complicate things and put iPad 3 on the share plan ($10 vs $15 is a no brainer?) and up the plan to unlimited voice and texting and shared 4gb data for all devices (iPhone and iPads). The woman even set it up to begin with start of next bill cycle (Jan 4) so no prorated charges. More perfect! Side note - Also asked about canceling second line and paying termination fee which would have been about $200. Seems like a lot but, given that I had a whole year at $34 per month to go, it's cheaper. Gonna think about that. So, I believe I have everything the way I want it until 23 December and a charge goes through for the 2gb plan ($30) I originally set up on the mini back at Thanksgiving. Somebody forgot to cancel it! I no longer have that original SIM to cancel it that way and decide to call them before it charges me again on 23 January. Figured I was gonna have to eat the $30. Finally called Customer Service again today to; a) cancel the original $30 iPad mini plan before it charges again, and b) cancel my other phone line and pay the termination fee which would be a savings of ~$100 over the rest of the year. First part was a piece of cake - cancelled AND $30 refunded that I was charged back on December 23. He had to send me to someone else to take care of the second line. First question she asked - "instead of terminating this why don't you just switch it over to another shared device at $10 per month?" Huh? But I don't have another device. "Not a problem," she says. "We cancel the share plan on the iPad 3 for example and then add it back by switching this line over to a share device." I'll take that! Only thing I asked was can start this for the beginning of the next billing cycle (I hated prorated charges) and she said she'd try. Comes back a few minutes later said "it's done, but I couldn't set it to start on 4 Feb so there will be prorating and I'm gonna credit you $25 to pay for that." Today's take - $55 off current bill and $24 savings a month for the remainder of my contract. I've never had anything but excellent signal coverage on my phones and now I am officially a HUGE fan of AT&T Customer Service!!!