Under normal circumstances, the Motivity app doesn't let you have more than one active job.
When you start a job and progress through to 'on site' stage, if you try and start another the app will pop up a warning to alert you to this fact.
If you do need the ability to have multiple jobs active then you will need to amend the mobile workflow configuration.
You need to switch off all the travelling forms in the Travel Screens
And in the Work in Progress Screens make sure only the On Hold and the On Site sections are enabled
NB - using this feature will mean office staff won't get updates about travel or on site statuses. They will only know when the job is completed.