What's the cheapest Mobile Internet plan w/ Data Stash?

My ZTE 4G LTE hotspot is kept around to just use when I go traveling for work.

I've had a steady $25/mo Simple Choice plan on it for a few years now, but find that I'm traveling less and don't need 6GB each month.  I hacer really appreciate the Data Stash: saving up those unused GBs pays off when I use it for a few days every 3 or 4 months.

I'd like to pay less per month since I've only used 1GB in the past 6mos, but still have that Stash for when I need it.  I'd love to drop to a 1GB/mo plan Ykeep my current (full) stash, but figure that’s too much to ask.

2GB/mo for $10 is just about what I'd like, but can't find any info if the 2GB/Mo Mobile Internet" plan still has a Data Stash or not.  Anyone know for certain?

Otherwise, starting to sound like a straight up prepaid company is better for my budget, since I don’t really see much benefit to staying signed up with T-Mobile (voice lines are on another carrier).