I forgot my samsung account

I have a samsung galaxy grand prime and i noticed that the device was not reading my SIM and I went to the store where I had bought it and the guy from the store did a factory reset on my phone and I forgot my samsung account because i made sign in with google account the only problem I have is i cant remember my google ID because when I was signing up for google I picked a username from the suggestions box and I forgot what it was ...... what should I do? Any options?