What good will it do in taking it to the service provider? You changed the code, only you know it. A new SIM card will not do anything since it is a phone lock, not a PUK lock. Only way to reset the phone back to the default code is to flash the phone's firmware. Use a search engine and research up on it, go to a cell phone repair shop to do the flash for you if you're not comfortable with it, then you can go from there. Also, if you intend on changing the code again, use something that you can remember easily.

i forgot the security code on my phone

its not the default 12345, what can i do now that i need to get a new sim card?

can i take it to my service provider?