Unlikely it needs a recharge.
First try this:
1) Start Car and set to LO leave until its cold inside
2) Turn up to HI and leave for 20 minutes
This may kill the bacteria.
Failing that, get yourself a can of Forte Air Conditioning Treatment (I find alternatives are NOT equal) and a new pollen filter. Remove the old pollen filter (from passenger footwell/ Glovebox) and do not replace. Follow Forte's instaructions and fumigate the car with the can and AC on full recirculation.
When the can has ran out and the car is thoroughly ventilated, fit the new pollen filter.
cars only need recharged if they have a leak, constant recharging is a scam - when was the last time you recharged your fridge?