There is one and it is behind the glove box.
Remove the glove box and find the recirculate intake door (move the lever between recirculate & vent and you'll see the door moving in front of you) - just to the left of that (assuming a LHD vehicle) you'll see a black plastic strip no more than an inch wide - it has clips on the top & bottom that hold it in place - unclip that and remove it and you'll find the cabin filter behind it.
You'll probably find it is choked with foam rubber - the rubber falls off of the intake door and gets trapped by the filter.
Something to consider - if you're getting airflow through the vents, the lack of heat most likely is not caused by a clogged cabin filter - you may have a "mixer door" problem or an engine running cooler than it should.
Coolant should always be flowing through the heater core as there is no "shut off" valve - what Suzuki does is control how much air flows through the core using a "mixer door".
i have very little wind coming out of my system so i know there is a problem there.the vent motor sounds very aggressively so that is good also, the thermostat is working fine as the needle stays at half wen running,but it may be not allowing the system to heat up enough. i do have a little bit of heat but not enough for sure. it defogs the windows a bit and thats all. and i do always use the outside vent as it always unfog the windows.
i had 2 cars before witch my problem was caused by the thermostat,my dad is a 30year + mechanic and solves that like nothing, the car engine temperature needle was at half and still i was getting barly any heat, my dad suggested me to change the thermostat and i dint listen (17 year old at the time and knew everything lol) i have change the heater core,coolant and still had little heat, then i have changed the thermostat and problem was solved, the thermostat wasent allowing coolant to flow enough to bring hot coolant to the heater core to heat up the car. as in winter the thermostat dosent let the coolant flow as much as its very cold outside
but this is my first car/truck with a air cabin filter, i figure the filter is plugged badly and stop the air of flowing, i want to remove it completely anyways as i will be in the woods most of the time and it will get clogged again quickly. also the previous owner got it stuck under a water hole after the front 4x4 air motor have failed and all the water went inside the truck, i have removed the carpet as it was ruin anyways.