If it's been no more than about three months since your sales call you can request a review of such to see if you were misled by the sales rep. If it's determined that you were you may have some type of recourse regarding the Early Termination Fee when cancelling the service. You can request a sales call review in the "myAccount and Billing" section.
Regarding your data, many devices can use data, even without you being aware of it. The following two threads may help you regarding your high data usage...
Edit: If you want to just straight up cancel you can call 866-347-3292 to do so. Please be aware that you'll be subject to an Early Termination Fee if you're still in a contract.
Hi Jpowel, welcome to the community and thank you for posting! I am sorry to hear you're experiencing issues with our service, and I'd like to see what we can to do help!
If you are noticing your data being used rapidly, you can perform our Data Depletion test here, then please post your results in this thread. Also, the links Gabe provided are very good references to help manage your data usage.
I located your account to run diagnostics, but I am unable to confirm if there are still any issues since you do not have any devices currently connected to your network. Could you please connect to your network so I can look further into this? Also to get a better understanding of your issues, can you tell me what you're using the internet for (streaming, Facebook, school, web browsing, etc.)?
Your cooperation, patience, and understanding are much appreciated.