Is that the only internet provider available at all in your area? That sounds like a terrible deal tbh. I also don't think providers charge for the amount of data you use, they charge based on how much data you can download over time (Megabits per second). IIRC my service through Xfinity is 200 Mbps (or 25 Megabytes per second) which works great because I only use one device at a time and never have issues with streaming. All that happens if your service is too "slow" is the streaming will have to buffer (pause) while it downloads the audio and video for whatever you're watching.
My neighborhood is semi-remote and one option I considered for a while was satellite internet which is available everywhere, just check the companies' reviews before picking one (I've read HughesNet sucks). Also if you happen to have 5G cell service in your area, T-Mobile offers internet through that for a good price.
