EastWest Bank's Maintenance Fee

For the past two months, EastWest Bank has been charging me a "maintenance fee" for supposedly falling below their minimum balance for corporate savings which is PHP20,000. The strange thing is -- I never go below their minimum. They cannot give any explanation either other than the sheepish "its system-generated" excuse. The branch manager is not of much help either as he cannot come up with any logical explanation as to why this keeps happening.

They are nice enough to always reverse the charges, but up to how long will this go on? I'm expecting another argument again at the end of this month.