Received 4 calls from this number today, the first of which was at 4.30am! Whoever it was left a voicemail,  but didn't actually say anything. They also texted me telling me not to call this number, they will call me back later, but not saying who they were or what they wanted. My Sync.me app says the number is based in Nigeria, that's all I know. I have now blocked the number. Presumably it's a scam of some kind.