Billing

You pay at the start of the service month, not after it completes. That is why it is to be perceived as "in advance" or "prepaid". You are not paying a month, weeks, or even a day before the service can be used.

Also keep in mind there is DirecTV and DIRECTV STREAM which are two separate services. You mention STREAM, but have posted in the DirecTV forum so I'll request the post be moved accordingly.

It’s DIRECTTV

Can’t be charged if you don’t have internet 

"Why am I being told that direct tv streaming"

"It’s DIRECTTV"

So which service are you talking about, DirecTV or DIRECTV STREAM? (and there is only a single 'T' in the brand name).

Can’t be charged if you don’t have internet 

Not entirely true. Yes DIRECTV STREAM needs to be setup through internet, but once done you can still be charged even if you don't have internet in the future. It doesn't automatically turn off as the service has no idea if you have internet at any given moment. It is subscription based, not usage based.

don’t tell me that directv streaming is prepaid 

That what the reps are telling me it’s prepaid service

It is only prepaid in that you pay at the start of the month, not after you've watched TV for the month.