How to Send Money to Your Interactive Broker's account for free

Hi all,
I’m wondering if someone else had a similar experience.
I’m with Migros Bank and used the CH IBAN (CH20 8909 5000 0105 6967 4) to transfer CHF from Migros to IB.
Migros told me that it would cost 5 CHF because the IBAN may be ‘Swiss’ but the receiving bank is most definitely not.
And they charged 5 CHF.