How does the caller get that number display & which country has that caller id?

I've received three calls from +8888 8888 today within the space of 1.5 hours - 1 to my home phone and two to my mobile. I am on the Do Not Call Register. Each time it went to voicemail and the caller hung up. After an internet search, I find there have been many complaints regarding this number and, if the caller doesn't hang up on the phone being answered, they claim to be calling regarding an old accident and associated insurance claim. Sounds like they're trying to scam personal information.

Call about a car insurance - offering to give me a bundle of unclaimed money for an accident I had within the last two years. Wouldn't tell me any details as it was a breach of privacy to do that. Explained that this money was a secret that the insurance company kept from me so that I never claimed it.