Missed calls from numbers I can’t reach back

[Esimmo]

Hi, this is my first time posting a question.

I have been receiving calls from numbers not stored in my phone, they are all mobile numbers.

I’ve missed the call and when I tried to call it back it doesn’t even ring, just rings off like it cannot connect to the number. Does anyone know what these are?

I have tried to pull them up on WhatsApp but no profile exists. Don’t know whether to text the number to find out?
I’ve had three in the last month. I’m very careful about who has my phone number so I know who is calling me because only those in my phone have my number so if my number has been given out I’d like to know so that I can deal with that or block.

Please help if you have any idea what this could be. Thank you. 

[AnnS]

Yes @Esimmo   These are spam calls being generated by a computer to random numbers and with some luck they will hit a live mobile number and the call will be answered or returned.

It is best to simply ignore any numbers you don't know.  See here :Nuisance Calls 

[Esimmo]

Thank you for your answer. What is the purpose of these calls? Why are they calling? Is it sales or something else?

[Esimmo]

Thank you @AnnS 

Thank you for your answer. What is the purpose of these calls? Why are they calling? Is it sales or something else?

[AnnS]

Hi @Esimmo 

It certainly won't be Vodafone calling, you can check the numbers Vodafone use from the look up tool here: Vodafone Marketing Preferences 

Not answering unknown numbers myself unless expected, wouldn't have the foggiest for the reason of the call, but it's your mobile number, you are paying for the service, the number is for your use and for people you know to be able to contact you.  These spammers have no business calling the number and trying to sell or spam you in any way.

If a call is not answered any genuine caller would leave a voicemail message.

[hrym]

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@Esimmo wrote:

Thank you @AnnS 

Thank you for your answer. What is the purpose of these calls? Why are they calling? Is it sales or something else?

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There will be very little that's genuine about them.   Assume that all they're trying to do is get personal information from you, possibly bank account details or credit card numbers for fraudulent purposes..   The numbers themselves aren't genuine and are spoofed to appear as if they are.  The actual source is usually outside this country.

[LaurieEdwards]

Hey! I'm sure they are scammers. They called me twice. I did not pick up.