When I transfer credits, it says that one of my bank deposits has been used.

"Deposits include placing funds in your account, or wiring it to another player's account."

It was the only way I could limit the transfer of funds and stop people using it to get around the bank deposit limit for their account.

Then can you at least get rid of the 15% fee plea?

Sorry not "plea", "please".

It is to make it unwise to cheat by piggybacking funds. It's also to discourage the movement of large sums without a penalty.

It used to be 30% until recently, so think yourself lucky

Honestly, I don't think 15% is that big of a deal.