Only banks above the provincial level of Bank of China can exchange foreign currency, and the denomination of exchange is limited. Small denominations and coins are not convertible.

Malaysian ringgit is a non-circulating currency, which may be out of reach of ordinary staff. You can ask their manager.

Finally, if it really doesn't work, and they all say it can't be exchanged, you can call the customer service phone of China Bank to ask about the exchange.

Intuitively, the business of the provincial bank you asked is not good. It should be one of the duties of China Bank to exchange foreign currency.