We usually have problems when we try to transcribe an Armenian name into English. Sometimes people have problems to transcribe an Armenian name into Armenian!
There are certain rules to follow.
Yes, indeed the name “John” might be transcribed as Ճոն or Ճան which depends on the phonetics you adopt, whether British or American. But if you have a child named Kevork and you want to transcribe his name in Armenian letters, there is only one to write it: Գէորգ. You cannot write Գէւորգ, Գեւորգ, Գեւորք, Գէւորք, Քեւորք, or Քեւորգ because he started to write it that way when he was four and his teacher did not want to hurt his self-esteem by correcting the spelling. The spelling Գէորգ has 1600 years behind it. Other spellings, however, are not that old.
The same rule applies to Hagop or Hakob (also Hakop). Unlike the case of Kevork, which entered the Armenian language after St. George the warrior, Hagop or Hakob (Jacob) is a Biblical name, and the Armenian translation of the Bible fixed its spelling in Armenian forever: Յակոբ. If you speak Eastern Armenian and your child’s name is spelled Hakob or Hakop in his English documents, that is perfectly fine, but that does not mean that his name in Armenian should be spelledՀագոբ or Հագոպ or Հագոփ. Again, Յակոբ is the only way to write it in Armenian; classical orthography, incidentally, is the official orthography of the Armenian Church. The spelling Հակոբ, on the contrary, has just 80 years, regardless of the fact that the Soviet Armenian orthography deviates from the tradition established by Mesrop Mashtots.
If you have a doubt about how to spell Armenian names in Armenian characters, it is good to reach out for help. Better to ask than to print 5,000 flyers or send 5,000 emails with the wrong spelling. There are still people around who will recognize when you made a basic spelling mistake.
As the saying goes, there is no shame in not knowing something, but the shame is in not being willing to learn.