What a phone number database actually contains
A catalog is a set of columns and measurement contracts, not a pile of digits. What each field means before you license one.
Every row is an identifier plus facts
A phone number on its own carries almost no commercial information. What makes a dataset useful is the facts attached to it: which country and carrier the number belongs to, which platform was checked, when that check happened, and what the result was.
That distinction matters because two vendors can both advertise ten million records while selling completely different products. One is selling ten million raw numbers. The other is selling ten million numbers with dated platform status. Only the second one can be filtered, priced per row and delivered reproducibly.
Status is a claim with a timestamp
A status such as valid, invalid or not detected only means something together with the moment it was measured. Numbers get recycled between carriers and reassigned to new subscribers, so a three-year-old validation result describes a number that may no longer exist in that form.
When you evaluate a file, look for the timestamp column before the status column. A smaller, recently checked dataset usually outperforms a larger stale one for any workflow where a wrong entry costs money.
Masking tells you what a preview can prove
Previews are masked for a reason. The free sample exists so you can inspect format, fields and freshness, not so you can harvest the inventory. A well-built preview keeps enough characters hidden that the row is useless as a working record, while still showing whether the value is a mobile number, whether it carries a country prefix, and whether the platform column is populated.
Treat a vendor that ships complete identities in a public preview as a warning sign rather than a bargain. Either they do not understand their own exposure, or they are willing to sell yours the same way.
The four questions worth asking
Ask for the column list, the coverage in your specific market, the median age of the check timestamps, and one masked sample row in the real delivery format. Those four answers reveal more than any headline record count, and they are cheap for a serious vendor to produce.