Declining an offer having already accepted due to a better offer

<p>I have been working part-time for a local company A as an Intern while getting my master's degree(Engineering) for almost a year. I really enjoy working there and there is plenty of growth potential.
I am about to graduate and up until one week ago It was very unclear, and I would even dare to say improbable, that I would be getting a job offer from company A. Due to the uncertainty with this company I started interviewing for other positions a few months back, and about two weeks ago or so I got a very nice job offer from company B. It is very close to graduation and having no other offers I went ahead and accepted the offer through email (I haven't signed any papers yet). A week ago (one week after having accepted my offer) company A offers me a job with a similar salary.</p>

<p>I prefer company A for personal reasons. How would be the best way to approach the problem? Should I email them? call them? I appreciate any advice </p>