Tom, just to clarify matters, you are not "dating" this girl. You are speaking to her on the phone and it's somewhat different.
If her parents don't want you to contact her just comply with their wishes. They may have a valid reason for insisting on this. You don't say whether or not you have ever met her (for real, I mean, not "online"). If not I find it very difficult to understand how much you love her. Hopefully you'll look back on this and ask yourself the same question. If she rings you simply hang up.
Whilst it is not a criminal offence to speak to her (unless your conduct can be interpreted as "harrassment" and that seems unlikely from your description) it can only lead to aggravation. If you can try to get out and about a bit. You never know you might meet a real live girl !