I bought a Happy Roaming for use in Guangzhou. It was impossible to roam at all. I had balance totally unused when I return. It was extremely disappointing and not trustworthy. I needed it for directions in Guangzhou as I have 3 elderly with me.
Network coverage and speeds when overseas is dependent on the partner network. Do try reinstalling the Prepaid APN using the Happy Prepaid App, switching to another roaming operator manually or placing your SIM Card in another handset to see if this helps resolve this issue as well.
You can also contact our dedicated Prepaid hotline at 9850 0000 for clarification on your concerns.