My account has shock free data and 500 mb monthly limit with an iPhone 6s. The last billing cycle ended January 17. On January 12th we got the 100% usage notification, which itself put the usage over the 500mb limit. We did not choose to add more data. Yet the data was not paused and we have been billed a 5$ surcharge.
Per the definition on your web site of Shock free data, data usage should be paused unless we choose to buy additional data.
This doesn't seem to be working.