This is a variation of "short number" fraud. Also abuses billing system delays/down times.
SMS2WMZ services are widely available (i.e. http://smsobmen.com/) and frequently used in these schemes. The prepaid numbers are main target in this case. Primarily small Operators with slow "balance update" are targetted. (there are known operators in Russia where it takes up to 30 minutes for them to "sync" balance. Nuts!)
- Abuse of "free balance" in exchange for registration schemes. (after balance is increased, it is converted into WMZ via such exchange points)
- Abuse of "pay via SMS" services.