Hi Nutty, welcome to the forum.
At the very worst, it could be that you're being called by a company trying to sell you something. You'll certainly not be charged/scamed by simply answering the calls, if that's your concern (incoming call charges may apply if you're abroad, though).
I would recommend that you answer the phone, wait until they've said who they are, tell them you're not interested in anything they're selling and ask them to remove your number from their marketing lists.
Another idea is to register your number with the Telephone Preference Service at
www.tpsonline.org.uk.
This will put your number on an opt-out register and should stop these unwanted calls. Although there are some unscrupulous companies who might ignore the TPS registration, in doing so they are breaking the law - make a note of their number before you answer, you can then make a complaint via the TPS website if calls continue after you've registered.
Hope this helps.
