Please I need help!!!

An innocent young looking guy came to my office to get a phone (Tecno Camon Cm) last week but didn't have cash so he wanted to make an online transfer to my account.
Shortly After I gave him my account number, he showed me that the transaction was successful on his Mobile app and even showed me the alert from his bank.
I waited for an alert to confirm the transaction from my bank but it didn't come.
Buttom line is that I allowed him to go because I saw what looked like an evidence of payment and felt maybe network was delaying the alert so i collected his Phone no.
After some hours and even till now I have not seen the money and have tried reaching the guy but he is neither picking up nor his number reachable.
Sincerely I don't know what next to do. I have dropped a couple of text messages for him telling him that the transaction failed and also begging him to come so we can sort it out but no responds from him.

Pls what do I do? If I cant get him to pay for that phone I will pay for the phone myself and its alot of money for me, because I am still a young guy trying to make ends meet for now.
Pls help a brother.
This is his no 08146800094 and this name is MICHEAL.

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