Email Security Issue

I signed into my email this morning and pulled up someone elses account info. Name, account number, everything. Scary. signed out, cleared my cache, signed in. Same thing. What is weird, I was in a email portal to pull up my email. Why did I get someone elses account info? i called tech support, which they treated me like I typed in the wrong email. Which was not the case at all. And what makes matters worse, this is a government account. They are currenty right now looking into it. Was on phone for three hours to try to report this security issue. And was treated like I Dont know how to type and the problem was on  my end. Not the case. I think the problem is on Verizon's end. Anyone else have problems like this today?