Smile [Q] Xperia Neo Pattern lock fix

Hello Experts,

I really need some help from you guys. I have a Xperia neo MT15. Recently I bought a new phone and I gave this Neo to my sister and she gave the phone back to me after a while. I didn't really use it for a while coz I had a new phone. But now when I tried the unlock pattern didn't work. Plus my sister doesn't remember it as well. I really need to unlock this device can someone please please help me ? I tried to flash but it says the phone needs to be allowed in debug mode or whatever. So there is no way that I can access up to that point and do such things. Can someone please tell me how to fix this issue. I would be really grateful to you guys if you could help me out. I'd be in your debt.

THanks