French to English Bus/Financial Telecom(munications)

From an agreement between an insurance company and a call centre operator.
"TITRE III – GESTION DES ADHESIONS
Le principe de vente retenu est celui de la « vente téléphonique en un temps »"
I understand the concept but am not sure how to phrase it.
The appendix contains a diagram showing how this "vente téléphonique en un temps" should be carried out. The call centre operator reads through a script and if the customer answering the phone agrees to the first stage they move on to the next stage until either the customer puts down the phone or agrees to take out an insurance contract. This process should be completed in one phone call.