How to disable outgoing calls only ?

[shonistalloni]

I usually fall asleep listening to a podcast or audiobook with the headset on but if the headset volume button or the phone's home button get pressed even with the screen locked, I somehow manage to call people with the help of voice control in the middle of the night. So my question is this: can I manually disable outbound calls only, or restrict it somehow and still be able to receive calls, texts and retain internet related capabilities? Or is there an app I could use. I can't use cydia apps since I won't jailbreak it again; and I can't ask the provider to disable calls on a schedule (I'm in europe). IOS 7.0.4