I'm on a $30 unlimited data T-Mobile family/friends plan. Since I'm not home a whole lot, I cancelled my ISP two months ago and have been tethering for two mon

I'm on a $30 unlimited data T-Mobile family/friends plan. Since I'm not home a whole lot, I cancelled my ISP two months ago and have been tethering for two months. I can still work for home just fine, and watch Netflix in HD. The speed is slowed down after 40Gb , and I get about 15-25Mb download speed.