culture conversion

How can you convert culture in a settlement which is originaly not your culture. I tried as Carthage to convert Syrakousa from western civilised culture to eastern culture. I stuck 3 generals, built punic-emporia and got to 98% eastern culture and 2% western in culture trens. But then the conversion seems to stop and I got problems with unrest in city. Also I couldn't build colony-punic (upgrade of punic emporia). There was no option in construction project for the city. Can culture conversion be possible? And if it possible how can you do it?

As I understand how things are, you need first to have goverment type which is not Regional allied tributary. That menas you must have at least Military occupation or Regional pacification or Stationary garrisoning or Local factional government in the city. Then you can build first own colony settlement, for Carthage is punic emporia. As city grows in numbers of population you can upgrade to colony-punic then to large colony-punic then to intermixed natives-punic. Each colony settlement has own cultural influence value (from 5% to 25%). When your cultural influence is larger than natives the city will converse to your culture. Mind you must be careful how you progress with colony upgrades to watch out on city unrest. If you upgrade to quickly you can have problems with large amount city unrest and you can lose the city. Also as Carthage you can build colonies only in cities with ports. And when you build colony settlement you can't demolish it.