Here's what I do with my phone:

• Nothing special, it is largely a stand-by phone and a timepiece.  It is a 10-yr old Motorola Razr with 2GB of space nearly unused because the volume is stuck on high and the battery is already so worn a 10-min call will drain it.  Getting a new battery = the cost of a new basic phone; so, no.
• I used to be on Virgin Mobile for four years on a $20/month ever 90-days prepaid and then went to T-mobile prepaid for six more years where I always got the $99 refill with 1,000 minutes/text for up to 365-days, but tend to used it up within 4-5 months.  
  • I figure it's because the phone is old, it gives me "delivery reports" on text messages I send to confirm arrival at destination-- as if back in the day, cellular transmission wasn't reliable and we weren't charged both ways for text messages as today. So the phone could go and I could keep the carrier, but it must be an unlocked GSM to reuse my SIM card.

Considering the carrier and my habits, I'm overpaying.  So far my research has lead me to Virgin Mobile's Custom plans.  I can configure to 250 min + 250 text and no data as low as $13/mo.  Except there are only three phones to choose from and I can't decide between LG Pulse, LG Unify or ZTE Emblem.
 
To be frank, my next phone doesn't need to be a smartphone, but I'd love to not have to turn the PC on just to access my 1TB WD Passport backup.  Can any modern basic phone access an external drive via a series of USB adapters?  Or is this an ARM vs. x86 issue?  Can basic phones with SD card slots take higher capacities than OEMs state, like 128GB or more?
 
If I could use a microSD card for my 11GB of music on any regular phone, I think I'd be set enough and save a lot of cash; current phone has no slot.  But then I hear battery life and performance with an SD card installed gets kinda slow, while the extra price for more onboard storage doesn't scale.
 
Any thoughts?  
 

 
Samsung S5 / AT&T.

I figured it was a longshot asking here, I know the track record; but I'm giving fletchj's "ting.com" website calculator some consideration.
 
The odd thing is I have a Tegra NOTE 7, which while could fill the niche I've created for myself, it is bulky and I don't want to damage it again.  I used some of my EVGA bucks to get it for cheap just to test it out a few months back, I never had even an MP3 player and I tried using it just for that.  But after a few months, it busted and sent in for an RMA.  EVGA sent me a brand new one, but I haven't opened it yet.  
 
If I could sell it, I could get a decent phone.  Except I'm no good at selling stuff and my phone budget is dependent on what and when the tablet sells.  Saving money from going to a different carrier could up the budget allowance, but there is no way I can afford anything Apple or Samsung or HTC or whatever the 'cool kids' get.
 
For now, my T-mobile prepaid still has $45 in it, so I could wait the next 2 months to drain it out and then revisit this idea.  But that is all it is, a bunch of ideas, and I have too many of those.

Have you tried ting fletch? It looks good, but don't they all. I dumped AT&T last year and have been happy with Virgin mobile monthly $35. I think they just upped the data to unlimited as well. Phone choices may be limited, not sure. They do sell a sim, but I don't know enough to be helpful there.

If you want to buy a used phone, http://swappa.com/ seems to be a safer source than ebay.