How long will it take for mainland mobile phones to roam in Hong Kong to receive short messages?

I am often in Hong Kong and Macau. If my mobile phone in Hong Kong and Macao doesn't have roaming in Hong Kong and Macao and international roaming, my mobile phone is just like an electronic watch and has no function.

Especially after Hong Kong passed the customs, there was no signal. (Macau may sometimes receive one or two messages) You can only use it after roaming in Hong Kong and Macao, and you can send and receive text messages and make phone calls. Receiving text messages is free.