The amount of data being transmitted depends on the services or apps that are currently in use. For example, streaming audio requires a great deal of data to be transmitted, which requires a good connection and a strong signal.
Cell phone to the vehicle
Connection speed may vary depending on the location of the cell phone in the vehicle. Move the phone closer to the center display to increase signal strength. Be sure that there are no obstructing/screening objects between the phone and the screen.
Cell phone to the network operator
The speed of the mobile network may vary depending on coverage/reception in the vehicle's location. Reception is generally poorer in tunnels, in mountainous areas, in deep valleys or indoors. Connection speed may also depend on the type of subscription that you have with the service provider.
Contact your service provider in the event of data transmission problems.
Restarting the phone
If you experience problems making a connection, it may to help to restart the phone.