Do not return calls to the telephone number +79407438115. It is an international premium rate number and calls will be charged at an extortionate rate. The number has been reported on Twitter by a user who complained about receiving a one ring call from this number. It may be in use as part of the wangiri scam.
Wangiri is a Japanese concept meaning one cut. It relates to this scam because recipients complain about being left a call from a completely unfamiliar foreign number. The call is cut after one ring. This is in the hope that the person who receives the call will phone them back. Anyone who does so will be connected to an international premium rate number. In order to avoid this you should delete the number and block the number.