Currently there are four major mobile networks who dominate the market, they are:
Pay-as-you-go
SIM cards are readily available to buy in shops and, providing your phone is unlocked, you should be able to get started with a network as soon as you arrive.
Try supermarkets, pharmacies or colmados (local family-run shops). If you want to get connected straight away, there are shops selling SIMs and top-ups across the road from the airport.
Prepaid SIMs are cheap and should come with some minutes included, though not many. You can then purchase a scratch card to top up - these come in lots of denominations, so you have freedom of choice here.
The pay-as-you-go format is by far the most popular method of communication in the Dominican Republic, meaning local rates are very good value. Remember that if you have a prepay SIM you will have to top up regularly to keep the SIM active.
Post-pay
If you call home frequently, it may be worth looking into a post-pay mobile contract. These often include free minutes, texts and data. Claro offer combined monthly talk and data plans from RD$995 and voice only packages from just RD$355. Their free minutes are valid for calling within the Dominican Republic and to the USA.
The same goes for Viva and Tricom, who have a post-pay plan for $240 per month, though this only includes 50 free minutes. Orange don’t offer any international minutes as part of their post-pay packages.