IPhone 4s jailbroken/unlocked & want to unjailbreak

I have a sprint jailbroken unlocked iPhone 4s that I am actually using tmobile with since its unlocked. I want to remove cydia so I can update my phone but I'm scared if I remove it that my service won't work since my phone is tmobile and supposed to be sprint. Will the tmobile service still work? & does cydia have anything to do with my phone being unlocked and working on tmobile instead of sprint?