The telephone number +351 3897 000 3645 is being used as part of a Wangiri scam originating in Portugal. The word Wangiri means one-cut. It translates to this phone scam because the scam caller will dial your number let it ring once then cut the call before you can answer.
The reason they cut the call is that they want you to phone back the number. Anyone who does phone back will be connected to an International Premium Rate Number (IPRN). Do not phone the number +35138970003645. If you get a call from this number do not answer.