Many businesses or products or services that share the same or similar trademarks are able to peacefully coexist. They operate in different geographical areas or they are in different businesses, offering different products or services. If a consumer is not likely to be confused by the dual use of a trademark, there is little likelihood of a trademark infringement suit. Consumers are unlikely to confuse ABC Warehouse with ABC News, for example.
Better than looking at "Rolling Stone Magazine" and The Rolling Stones, you may want to check out the
Apple Corps v Apple Computer trademark infringement suits. Although they have seemingly worked out an agreement now, they spent many years and countless thousands (millions) of dollars fighting over their dual Apple names when their similar products/services were marketed to the public.
I agree with FlyingRon and HomeGuru.
If you have been contacted by a company operating under the same name as the one you are using, you have limited options. Have Safari Rangers, Ltd. provide you with proof they were first to use the mark in commerce and that they have rights to the name in the U.S. If the name is not registered in the U.S. and they are not in business in the U.S., and you have no plans to expand into South Africa (or whatever other countries Safari Rangers, Ltd. may have their name registered or may do their business), then there should be no problem with both of you using the name for different purposes. . . .
. . . except, of course, for the problem that Safari Rangers, Ltd. may seek to stop you from using the name by filing an infringement suit against you in the U.S.
Whether Safari Rangers, Ltd. could get an injunction is a question mark, and depends on all sorts of facts and factors best reviewed by an IP attorney in your area.
Good luck.