Have all pay per use plans been discontinued?

As an expat living outside of the US for nearly 10 years, I've used and loved having AT&T PREPAID service. It easily allowed me to switch SIM cards and instantly have phone service when traveling back to the US.  When aboard I would always keep my plan set to $2 per day (a pay per use plan). This allow me to keep my balance and not pay for US phone service when aboard. For short visits, I would just leave the plan at $2 per day. For longer trip to the US, I would switch to a monthly plan. After leaving the US, I would switch back to $2 per day until my next trip. 

Before my latest trip to the US in April I switched to $30 monthly plan. After my trip I no longer had the option of switching back to $2 per day. I'm not enrolled in autopay but still had $30 deducted from my account in May. (I now see this in the fine print of the plan details.) 

Have all pay per use plans been discontinued forever? If so, is there any other option I could use to put my account on "hold" while overseas?

What happens if I let my balance expire? Would I loss my account and phone number? Would the account be waiting for me to make a payment when I want to start using it again? Would I be charged for unpaid months (despite not using any service those months)?

I'm not interested in paying $360 per year ($30 monthly) to have phone service for the 8 or so weeks I might be in the US each year.