Hello,
Yes, I was able to call to that number in Vietnam using 00, but wasn’t able to call using 011. Like I mentioned, I tried many times with the 011 and 84 but could not get through. My cousin had to ask the phone company in Vietnam and that is where he gave me the answer to use 00.
I’m not sure if it is the complete number or not. I received two calls from that number and that is how it appeared on my phone. Are there any phone numbers that start with 852 in Vietnam? Thanks again for the reply.