I had a terrible experience with Verizon recently. Last month they showed my wife's phone suddenly was 3 GB over normal usage. Nothing changed, but her mobile data skyrocketed and we were charged 2 GB over our limit. I was on a business trip and over 1/2 of those I spoke with said they too had a spike in data usage.

New month hits and 6 days into the month, I get a note we have used 6GB of data. I call Verizon and their answer was simple, my daughter is using more data on social media and that's the cause and we should consider going to unlimited data.  After we spend hours on the phone and chatting with tech support I get the same answer. We look at data usage since 10/25/16 and it shows 19 GB of data, equal to what we were charged per month. Surprisingly the 6GB of data for the past 6 days don't add into the equation. I advised I think they are opening themselves up to a class action lawsuit with this kind of actions. My daughter talks to the rep and said they tried at least 8-10 times to get her to switch to unlimited data. It's preposterous. She was on wifi the entire time, and the data usage for the one day we discussed was 1.6GB at 6:39 am, when she was sleeping! They kept saying there were apps using her data, yet no app had near the amount of data usage. There is a scam going on and millions of customers are switching to unlimited data to stop this.  I had to escalate my call and they wanted my daughter to back up her phone and erase everything and start over. Something is quite wrong here!