Mine has started saying: "You're using the original charger, please re-connect to charge faster." I unplug it and replug it, and it says "charging" but it's been doing a horrible job lately.
It's a fairly new ZTE phone, with a C-plug. I contacted support, to see if my other charger would work, and they wanted all kinds of info. They also kept saying "use authorized ZTE equipment only."
So I ask for details on getting one, and they say they don't carry one like that. Then my phone started giving me that original charger message, and stopped holding a charge for very long. Coincidence? Maybe..