There are absolutely ways to intercept a call from a targeted user that would be viable to use to gain access to a mid to high value user's funds.

SS7 call routing and rogue 2G base stations are some potential approaches.

In terms of banking security, a good (ideal) architecture would treat the user PIN as a credential which is not transmitted over insecure means. Unfortunately many banks don't do this right, and still support bank-side PIN verification (with the PIN sent over the wire to the bank), rather than using the bank card's smart card features to carry out on-chip PIN verification.

If you built a bank from scratch, for security first, you'd likely still use smart cards as bank cards, but you'd only do PIN verification on-card, so the user PIN is never exposed to even the bank - the card can securely vouch for the PIN in a manner that's far more costly for an attacker to defeat than using a $5 wrench against the user of the card to make them reveal the PIN (h/t to XKCD).

Sending the card number and PIN over the phone is just asking for trouble - mobile phone calls are decrypted at the base station and available in the clear, before being transmitted up into the wider telecoms network.