temprature went from hot to cold while driving

I have two suspicions. One possibility, that the thermostat is failing and causing the engine to get hot and blow coolant into the reservoir, that causing the gauge to show cold when the coolant level is below the sensor. The other worse possibility is that the head gasket's failing, causing the same symptoms as I've described above for a failing t-stat. You can get a technician to check for combustion products in the cooling system which would indicate a blown head gasket. If you work on the car yourself, maybe replace the thermostat first. Don't allow anybody to sell you a 'cooler' t-stat, that won't help you. You want the engine to run at the right temp so get the specified t-stat. If you want to find a Mazda specialist, here's a directory link for you: https://repairpal.com/mazda-repair-in-brandon-florida