How to reset my locked iPhone 4s?

So my ex changed the passcode on my phone, and I have no clue what it is, and have been trying for days now to figure it out… Is there anything I can do without going to the Apple store? I don't have one near me, so I'm trying to see how I can just reset the phone, but I haven't found a solution as of yet.

The suggestion to hold the home & lock button for five seconds does not work, because this is the 4s, that just brings up Siri, and doesn't do anything to the phone.

Any suggestions?

You have to plug it into iTunes then go to your iPhone and then do "restore" and it will wipe everything out including the password