How to eavesdrop on your conversation?
It can be assumed that the phone in the switched off state transmits some data to the operator, and the operator - to the bank. I think that in this case you would notice at least an increased consumption of the battery.
Where to store all this data?
If you listen to all subscribers in this way , and not specifically you (why?), imagine what kind of network load the mobile traffic of millions of people would create 24/7. Additional costs are needed for the storage and analysis of the recorded audio information, which, most likely, is only planned to be introduced in connection with the notorious "Yarovaya law".
Are you being followed?
Banks, of course, use some information from operators for their own purposes. For example, data on the location of the subscriber (in relation to mobile towers). If in your credit questionnaire you indicate that you live and work in Moscow, and you yourself constantly hang out in the village of Kukuevo, then the fraud will be revealed and you will be denied a loan.
How to get more data from you?
Before talking with a friend, you may have left evidence of your interest in travel and loans online or in email. Banks will be happy to buy filtered data on Internet traffic with words of interest to them, such as: "bank", "credit", "travel", etc. This approach is much more effective than total surveillance of everyone around.
The cards that are imposed on you are always some kind of bullshit. Coincidence or not is not important. The card needs to be issued only by yourself at the bank.
In general, yes, a coincidence.