Importing contacts from old dumb phone
One possible option, if you can be sure which 150 contacts are being copied to the SIM in the old phone, is to transfer 150 contacts, copy them to the smart phone, and delete them from the old phone.  Then, next cycle, you'll get the next 150, and in twenty minutes or so you'll be done.  The trick is being sure you're deleting the same contacts that were transferred to the SIM.