Toll-free numbers are allowed as long as your country code is included. The reason is that toll-free numbers without country codes cannot be uniquely identified — the same number can apply for two different countries.
Also note that there are added complexities around toll-free numbers. Typically, if you call a toll-free number with the country code when you're inside the country, it will fail. This means that there is a chance your customers from your country will try to dial what shows in the business contact (country code included) and they won't be able to reach you. If this is a concern, you will need to let them know explicitly.