Hong Kong Mobile Carriers are getting worse. Which carrier would be better?

Which carrier would be better?

I used to be Smartone subscruber. But the stability degraded over the past few years a lot. In the past, though not stable, but I still can use mobile data to connect to the internet. But later, I cannot connect with mobile data in my work place and at home. The worse area is along mtr. I have tried to connect to google.com at Kwun Tong station but even when I got off at Tsuen Wan, I still cannot show the page.

So, I changed to subscribe China Mobile as I can use mobile data even in China. But this even worse than Smartone. Connection when travelling on MTR can never be achieved.  Most areas in Hong Kong cannot use mobile data, Tsuen Wan, Kwai Chung, Tsing Yi, Mongkok, Tsim Sha Tsui, Wanchai, Causeway Bay, Ap Lei Chau, Admiraty, Cental, Yuen Long, Tin Shui Wai (where I am now writing this blog, there is no data signal).

I. have heard that CSL would be the best, BUT their fee is also supreme.

So, is there any economic plan/carrier that I can subscribe? There is no need to be fast. I only want coverage.