Seroflo is Salmeterol
while Formonide is Formoterol
. So on the face of it, they appear totally different, but they contain combination of same groups of drugs - Bronchodilator: Salmeterol, Formoterol + Corticosteroid: Fluticasone, Budesonide. Hence they have same mode of action with subtle differences regarding potency, efficacy.
So your doctor might have changed your prescription from Formonide to Seroflo if you have not been responding well enough to the former. But the pharmacist cannot substitute it.