Is Sprint cracking down on data usage?

[xxxjdoggxxx]

Today I received a letter from Sprint about my roaming data usage. The letter is attached (sorry I don't have a scanner so I took a picture of the letter with my phone, it's readable but blurry) Basically it says I am in violation of the roaming terms and conditions. I have unlimited data and roaming is included in my plan. The only time I ever use data on roaming is when I go up to Michigan to visit family which is maybe a couple times a year (there is no Sprint coverage in Upper Michigan). In previous years I took my laptop and tethered with my phone. The last time I went up there however I forgot my laptop and didn't do any tethering. Just some browsing and netflix on my phone. Has anyone else received a similar letter? Should I call Sprint and ask them what the issue is? The letter says my account is being monitored now. Does that mean basically no more tethering for me?