Joke Collection Website - Public benefit messages - What should I send to 186 for China Mobile, Shanghai and mobile integral to exchange phone bills?

What should I send to 186 for China Mobile, Shanghai and mobile integral to exchange phone bills?

Shanghai Mobile: SMS channel sends HFXX to 1658999 for exchange.

XX represents an amount such as HF5 to 1658999, which can only be exchanged once a month.

The exchange amount is HF3/HF5/HF1/HF3/HF5.