Most people in
The company began the service since 1997.
I joined the company since April 7, 2003.
What they actually mean is:
The company began the service in 1997.
I joined the company in April 7, 2003.
The correct use of “since” is as follows:
The company has provided (or has been providing) the service since 1997. (The meaning is that the company began offering the service in 1997 and is still offering the service today.)
I have been a member of the company since 1997. (The meaning is that I joined the company in 1997 and am still an employee at present.)