Compromised Credit Card

[Subtitles]

My credit card has been compromised. I have no idea how did this happen as I never let my physical card out of my sight and I never do any transactions using my mobile phone and the card wasn't stolen.
I check my credit card transactions on a regular basis and early this month I noticed three payments to the same restaurant on the same day (my guess is it was a take away payments giving my credit card number by phone). A total of $210
I reported it to the CR company and asked to cancel the credit card and to issue a new one with different card number.
Hopefully they will credit me with this total amount.
I have been trying to figure out how can this happen, even with my precautions.
The CR has a set of 4 x 4 numbers. The last 4 numbers are always shown on invoices but the first 4 numbers are also well known as they are quite common numbers. So this leaves the second and third set to guess right.
Then there is the CVV to consider how did they got hold of it.
Assuming I will get the refund, will the restaurant lose money on this payment or they are also covered in such cases?
I think 4 x 4 set of numbers is not enough and they should increase it to 4 x 5 digits. Microsoft Windows 11 use 4 x 5 sets of digits.

Has anyone been in such a situation and what was your experience on it?
Do you have any suggestions how to increase the security of credit cards? Should I get a notification to my mobile phone and request to approve for every online transactions for example?
Thanks for your suggestions.

[ProWo]

I don't know if they exist in your country, but there are reloadable credit cards that you can use for online activities.
This way you can always charge the amount you need and after the transaction the available amount is back to zero.
So abuse is ruled out.

[Subtitles]

Yes we have such cards, but they have some limitations that I don't like. I prefer the regular ones.

[betwixt]

Look up "Luhn algorithm".
It's the way card numbers are checked but given half the digits it isn't difficult to work out valid combinations of the others, although not necessarily finding registered cards. The CVV can't be calculated, it is issued randomly. Almost certainly somebody leaked your number when you gave it them.

Brian.

[pandy]

Well - you can always start charge back procedure if you disagree... I can always invalidate my credit card - in my country there is dedicated service for this active 24h per day - i assume nowadays each bank offer similar activity.
Normally if you think that there is some kind of abnormal activity then you should contact with police and raise complains - they should investigate such thing - this is almost for sure law violation pursued automatically (at least accordingly to penal code in my country).