A method comprising: Receiving a user request from a mobile device to configure a mobile user account pre-provisioned with one or more virtual private branch exchange, PBX, services including receiving user configuration data for configuring the one or more virtual PBX services; configuring the one or more virtual PBX services based on the received user configuration data including configuring one or more conversion rules for converting communications originated from or destined to the mobile device into different formats; receiving, by a first provider, a user communication in a source format intended for a recipient from the mobile device, the user communication sent using a source communication portal; determining, from the one or more conversion rules, that the user communication is to be delivered to the recipient in a destination format, wherein the destination format is different from the source format; determining that accessing an external communication portal associated with a second provider different from the first provider is necessary for the first provider to convert and deliver the received user communication to the recipient in the destination format, wherein the external communication portal is a communication portal that is used to send communications in the destination format, and wherein the first provider is unable to handle the destination format; in response to the determining, delivering, by the first provider, the received user communication to the recipient based on the source format and the destination format including: obtaining authentication data for the user account of the sender of the user communication with the external communication portal from the mobile device; accessing the external communication portal, wherein the accessing comprises accessing the user account of the sender of the user communication with the external communication portal using the obtained authentication data for the user account; and delivering the received user communication in the destination format using the external communication portal. Receiving a user request from a mobile device to configure a mobile user account pre-provisioned with one or more virtual private branch exchange, PBX, services including receiving user configuration data for configuring the one or more virtual PBX services; configuring the one or more virtual PBX services based on the received user configuration data including configuring one or more conversion rules for converting communications originated from or destined to the mobile device into different formats; receiving, by a first provider, a user communication in a source format intended for a recipient from the mobile device, the user communication sent using a source communication portal; determining, from the one or more conversion rules, that the user communication is to be delivered to the recipient in a destination format, wherein the destination format is different from the source format; determining that accessing an external communication portal associated with a second provider different from the first provider is necessary for the first provider to convert and deliver the received user communication to the recipient in the destination format, wherein the external communication portal is a communication portal that is used to send communications in the destination format, and wherein the first provider is unable to handle the destination format; in response to the determining, delivering, by the first provider, the received user communication to the recipient based on the source format and the destination format including: obtaining authentication data for the user account of the sender of the user communication with the external communication portal from the mobile device; accessing the external communication portal, wherein the accessing comprises accessing the user account of the sender of the user communication with the external communication portal using the obtained authentication data for the user account; and delivering the received user communication in the destination format using the external communication portal. obtaining authentication data for the user account of the sender of the user communication with the external communication portal from the mobile device; accessing the external communication portal, wherein the accessing comprises accessing the user account of the sender of the user communication with the external communication portal using the obtained authentication data for the user account; and delivering the received user communication in the destination format using the external communication portal.