As salaamu alaikum ustadh, My friend argues that informing others about a person's birthday is not haram as they technically did not wish them. I told him that this is not allowed. Was I correct in doing so?

This depends, if he is just informing that i was born on so and so the year so and so, then that's fone he is correct. But, if he is saying this to remind people of the occasion and to celebrate etc then this should be avoided.