i needed to make few phone calls from Singapore to UAE. which one is best?

The calls are not cheap. The rates range from a
low of 17.2 cents US with WORLD MIDDLE EAST,
to 18.0 c US with COMMUNICATION FIDELITY
and upwards from there to 27c US.
There may be others around the street corner that
sell a few of the unkown kind for a discount. But the
quality of sound is not assured.
So, be guided by this.

Freddie