The Wells crashed out of the FA Vase with a shot shy performance at The Culverden.
Peter Dean gave Southall the lead after half hour with a blistering strike from range.
Aaron McLeish added a second on the stroke of half time.
With time running out The Wells looked to rally and Josh Froggatt pulled a goal back with 12mins remaining.
There was to be no equaliser though as Emanuel Dosho capitalised on a defensive error to finish coolly on 80mins.
The Wells traces to K Sports on Saturday in the first round of the Kent senior trophy.
Kick Off 3pm.