Are you sure you've hit your soft-cap before? There's a huge diff when a carrier throttles you once you've hit your limits and you would know when it hits you, even when you don't get the SMS alert warnings. In this case, Wind Mobile throttles down to 32 kbps or slower once you've hit the 5GB limit, even coming from 1 Mbps is a huge diff and you would had known about the soft caps before I've stated it.
I've been throttle before on T-Mobile US with their 200 MB LTE and 2G "unlimited data" on their $3.00/ daily prepaid passes in the US. From speeds of 83 Mbps throttled down to even 1 kbps a few times, both the IP5 and IP5s got warm loading all that data at those speeds. I even had to turn off my cellular data to preserve my batt life in NYC.
Technically speaking, that ain't unlimited data when they throttle you to unusable speeds and kill your batt life to honor that gimmicky marketing and especially when you have a AWS network that doesn't even have enough towers to handle such a small amount of subscribers.