3 phase converter query? What is the cheapest/most efficient device to convert a delta phase (208)...

What is the cheapest/most efficient device to convert a delta phase (208) to a 120 volts??
We only hold 70 amps ,(#4) coming in through the 120v feeds, and yearning to increase the total amperage possibilities,and were wondering if we could transform or convert the 208v to 120v, and what device would be the best to accomplish this?
A/C blowing but not cooling!?
Lots of possabilities. You need to tell to an electrician.

Just turned on insubstantial within kitchen, its acting...
I think you will find it cheaper to get better service installed than to return with a transformer of significant amperage to convert the 3 phase to 120 (unless, by some chance at the edge of my ignorance, respectively branch is 120 with respect to ground - 208 to each other).
Is this living station? In your city, like mine (Dallas TX) home owners may take a check to do electrical in their own home under a travel document but without a licenced electrician. I cut the main lines myself (if the power company have done it, it would have remained off until inspected and they put it back) and installed a hot meter box and 200 amp service doing a temporary reconnect until inspection and the power company changed my temp to permanent. You may be capable of install new service beside the old or replace the behind the times as I did without full price electrical work. If there are single 70amps coming in you will have to consult your power company. The cable size is maxed out as per the amprage coming in.
My 1st home?
Answers:    a transformer would be the only mode. not necessarily cheap.