Some retired Birmingham employees are at City Hall today with questions about  increased healthcare costs. City retirees got a letter on Friday telling them the rate hikes will take effect in less than a month. That letter came after an earlier notice assuring retirees their rates will not be changed. Single ratepayer coverage will go from $164 to $356 per month while family coverage will go up to $1,100 monthly. Co-pays and deductibles are also expected to rise. Some retirees say the city has taken away an agreement it had with its retired workers without any explanation for making the move.