is the micro-mail phone book free? How does the telephone Book of micro-mail charge?

Introduction, in fact, this call is not required to charge is free phone, but the need for traffic costs, this is not a micro-letter phone book collection and your operator to collect your money,

Micro-letter Phone book in the 2G/3G/4G Network for a minute to consume about 300K of traffic; less than 1k/hours are consumed during the time; After successful registration, the first automatic backup of the contact requires a small amount of traffic (backup 300 of the contact needs to flow around 60K); new/deleted/modified contacts will automatically back up changes in the data, A single contact consumes 0.2K of traffic.

At present, the carrier traffic rate of 1K roughly between 0.0001 to 0.0005 Yuan, based on this price conversion, the use of micro-letter telephone in the 2G/3G/4G network under the call for a minute to spend about 0.03 to 0.15 yuan.

Question and answer, do not know if this can be in the WiFi network to make a phone call, if it could be so very much the Hua-oh.