The written form requirement for the arbitration clause is satisfied where the parties' intention appears from a written document, even if unsigned, provided that acceptance thereof is unequivocally established by subsequent conduct or by the production of the document itself in proceedings to assert contractual claims. A party that disputes the absence of a signature on the contract containing the arbitration clause but relies on the same contract to bring proceedings against the other party cannot avoid the application of the clause itself.
The existence of an arbitration clause does not exclude the jurisdiction of the ordinary court to issue a payment order, given that the rules of arbitral proceedings do not provide for the issuance of ex parte orders, but requires the court, in the event of a subsequent opposition based on the arbitration exception, to declare the opposed order null and simultaneously refer the dispute to the arbitrators.