Shenzhen_on9

You can also check 12voip.
Calling Hong Kong and China is Free in the Free period.

Shenzhen_on9

Mr. Tom.
I created my account on 12voip by down-loading to PC, and then run the program. At that time, I used PC for calling.

I know that after getting the ID / password, you can use it on ATA or Android SIP client.  

You need to recharge once and you will get 90 days free period allowing you to call one of the free country for free, including HK, China, etc.  After 90 days, your credit will expire and you need to recharge again.  Min recharge is 10 USD.
I used it long time ago, and I got some credit after initial registration.

You can compare the tariff of all major VOIP operators.
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Shenzhen_on9

The following VOIP operators are offering FREE calls to Hong Kong and China. Some of them can give you SIP Access as well.

12voip
Jumblo.cn
Smartvoip
voipblast
voipgain
voipzoom

If you recharge for 10EUR or 10USD, you can call for free in the free period for 90 or 120 days.

Shenzhen_on9

free call, 是没有什麽限制. 这是说不能超过几万分钟. FUP (公平使用政策).  
10美元, 几万分钟 - 价格是非常低的. 但是效果一般.

撥號rules好似是美国的Dialling rule.  
0086 打中国. 00852 打中国香港.

Shenzhen_on9

是 12voip.com 和其他  Betamax 的产品.  
声音是一般呵.