Can I still get charged for data if I dont use my sim card?
If you have a contract, the fixed monthly fees will still apply (if you use it or not) with SIM installed or not.

If you do not use your mobile data (true your carrier) but use free WiFi, you will not be charged any fees for that by your carrier.. 

You can always go into your Cellular settings to turn off data which will allow for you to receive phone calls and text without the use of data.