"Is any SMS/phone call coming out of your personal number something you should consider private from the government? Probably not."

Well your phone calls themselves -- the actual conversation -- shouldn't be accessible without a warrant for a wire tap, that's pretty longstanding precedent in the U.S. Cell phone location information is also protected by a warrant (Carpenter v. U.S.), but pen registers (logs of who you call) do not require a warrant (Smith v. Maryland). I'm not sure if governments are prevented from purchasing data from carriers, just as any data broker could do. Additionally, who knows if governments are secretly collecting phone call and cell phone data and storing it, but only accessing it once they have a warrant. It's impossible to know what's fully happening on the back end between big telco companies and the gov't.

Either way, at the end of the day, whether you have Cape or some other service, if you're at the level of the government getting a warrant for your data any legitimate company is going to comply. That's why the best thing is to have a company that can only turn over limited amounts of data because that's all they have.