The company was founded in May 2005 as a joint-venture with E-Plus. Its headquarters are in Düsseldorf led by Nicolas Biagosch, the current CEO. The success of the pioneer Tchibo late 2004 (in a 50-50 cooperation with O2) and Simyo's entry into the German mobile telephony market in early 2005 were followed by several similar offers from other low-cost provides around mid-2005 resulting in a general price decline in the German mobile market.
The German provider Mobilcom first tried to stop Simyo with an injunction, as E-Plus hadn't granted the same conditions to other providers and hadn't given sufficient notice about the start of the mobile offering. The Federal Network Agency (BundesNetzAgentur, formerly RegTP ) decided this case on July 12, 2005 in favor of Simyo, and justified this by saying that:
"The simyo offer was not simply a new tariff, but a new product. In light of its commercial, technical and marketing philosophy which has renounced costly, hitherto widely found features, it differed in essential details from conventional prepaid products."
On 3 January 2007, E-Plus announced the complete takeover of Simyo. Simyo does not own a wireless network but, as an MVNO, uses the network infrastructure of its parent company. In May 2010, Nicolas Biagosch took over as CEO from Rolf Hansen. Simyo is part of the E-Plus Group which has 22.7 million subscribers (Dec 2011).
Simyo belongs to the Dutch telecommunications group KPN, the fourth-ranking mobile telephone operator in Europe, after acquisition of the remainder of E-Plus on March 14. 2002. In Spain, Simyo has been operating under the trade name of Simyo as an MVNO since January 29, 2008 through the Orange network. KPN sold its stake in Simyo France on December 22, 2011  to Bouygues Telecom, KPN's main mobile partner in France.
Simyo bases its business strategy on "Self-management via the Internet", using a model similar to that originally made popular by online banks. This business structure permits considerable cost savings, which the operator passes on in its rates. Another aspect that helps to cut costs is that they do not subsidise terminals.