They can still apply charges to your account even if they are not allowed to take it out of your benefits - it will just mean that you gp further and further overdrawn. Best not to incur any charges in the first place:
Social Security Administration Act 1992
Miscellaneous
Certain benefit to be inalienable **
187- Subject to the provisions of this Act, every assignment of, or charge on-
(a) benefit as defined in section 122 of the Contributions and Benefits Act;
(b) any income-related benefit; or
(c) child benefit,
and every agreement to assign or charge such benefit shall be void; and, on the bankruptcy of the beneficiary, such benefit shall not pass to any trustee or other person acting on behalf of his creditors.
** inalienable = not to be forfeited.
The effect of this legislation is to make it unlawful, regardless of any terms and conditions imposed by the bank upon an account, for you to take charges from any money deposited which is solely consisting of Social security benefits.