Unfortunately the bank doesn't offer a way to send them secure massages. Neither via their web interface nor via HBCI even though they drop their customers messages into their online post box, which I find pretty unfair. So the only way for mi to send secure messages is via snail mail (!!!). Other banks have digital 2-way-communication. Doing it by phone is unnecessary complicated for me.
Also they don't offer standing orders with "ultimo" option, so that it will be executed automatically the last (bank) day of the month. Other banks do that and would be important for me.