I am not a bishop and i am not a deacon. And I think you aren't it too.Verse 12 also says that deacons - anyone who serves in the local church - must also be a husband of one wife.
The bible has never forbidden polygamy. The law of Moses in which all laws are included has never forbidden it. Also the NT says nothing about it, never does the NT say: You need to have only one wife or You are not allowed to have more than one wife.
The great prophets like Gideon, Abraham, Jacob... had many wives.
But what the bible says is not to have too many wives, so that your heart become bad. It is like wealth if you have too many wealth your heart become bad too.