Strange Phone Call Numbers

[#1]

I not sure if anyone else has experience this or can offer any solution. I have started to receive phone calls from numbers such as 011 and 0818. These are very odd numbers and not sure what I can do about them and who to report them to.
I am not ex-directory but I am registerd on Telephone preference Service. What the heck are these numbers ?
With thanks

[#2]

The 0818 *could* be Sky.

[#3]

011 could be some kind person from "Microsoft" who wants to fix your computer and steal your bank details.
http://forums.digitalspy.co.uk/showthread.php?t=1530043
Caller IDs can be spoofed so it could be anyone. As the numbers are invalid the assumption should be that whoever they are they are up to no good. (By providing a bogus number they get past Anonymous Call Rejection)

[#4]

Thx for the replies. It was kind of what I figured. I will just not answer the phone to those numbers anymore.
The next question is how do I report them and who to ? The ones I have answered have been silence on the other end so I don't know who they are

[#5]

Is this of help?
http://is.gd/llWhDT

[#6]

derboff,
If you're registered with TPS you can raise any unsolicited calls with them: http://complaints.tpsonline.org.uk/Consumer/