I have a 2000 Mazda Protege that experienced an unusual issue this morning driving to work. I was driving at highway speeds (65 MPH) when suddenly it felt like the car roughly downshifted. The RPMs went up over 4000, then came back down and the car appeared to get back in gear (not sure if this was because I took my foot off gas initially). The check engine light came on and the OD off light began to blink. I slowed and was preparing to exit the highway at the next exit when about 2 miles down the road there was a sudden shift, like the car roughly up-shifted and the the OD off light stopped blinking. The check engine light remained on.
This happened on previous time and our garage charged a princely fee to check the code and flush the transmission and called it good.
Any help would be appreciated.

 

Ok
First, take it one of autoparts chains and get the code read. That will tell us where to start. You definitely have a transmission issue. But we need to know where to start.

When was the last time you had the transmission fluid deep flushed. Not just drained. If it's been more than a year, then it is time to do it again.