There are plenty of reverse phone look-up services that will reveal what type of provider and the name of the carrier for landlines and cell phones. My favorites for these are www.phonelookup.com and www.phonevalidator.com. But what if you need to know the provider for a “toll-free” number, so you can obtain subpoena data? Well I have seen these types of sites come and go pretty regularly, but my current favorite is www.customtollfree.com.