Extending TIP

In Zihuatanejo, I just received my Residente Temporal from INM and now I need to extend my TIP from 30 days to a year. I had understood that I needed to go to the Aduana to accomplish this, but I talked to them at the airport yesterday and they said they don't do that...that I have to go back to Tijuana where I originally registered the car. I know that isn’t correct and after some research, i think Banjercito is where I need to go and it looks like the closest one is in Lázaro Cárdenas. I hope someone can give me some advice on this. the 30 days is up on the car on the 27th of October. thanks mucho.