If this is someone else's fire wall, you need to Counterspell it, and you can't really redirect the energy.
If this was an environmental condition that the GM set up for other reasons, and all you were doing was damaging someone else, without taking down the wall of fire, then in this situation I would have cast a fire Evocation as normal, and then free-tagged the "Wall of Fire" Scene Aspect (or Zone Aspect) for a +2 to the Discipline check.
The GM may not have made it an official Scene/Zone Aspect, though - he should allow you to Declare it as an Aspect - it's right there. Should be a free Declaration, no skill roll involved. This is the sort of environmental awareness we want to encourage - people using what's available in the scene.
If you wanted it gone, and it was an Aspect, you just need an opposing Evocation Maneuver to cancel out the Aspect. The GM sets the difficulty for that.
Now, if this was a Zone Border you wanted removed or bypassed, like making a door, then I would have run it as Evocation and asked for enough shifts to equal the value of the Zone Border, plus shifts for duration if multiple people across multiple Exchanges needed to pass through it to escape.
And if you wanted to do both? Open that door AND attack enemies with the section of fire you "tore away" you'd either need to either impress the GM and let him have you cast both at the same time, which is a LOT of Mental Stress (but sounds heroic). Or, you would:
Exchange 1: 4+ shift Evocation Fire maneuver to place Sticky Aspect "Tear in the Fire Wall" - allies tag it for a +2 to their Athletics checks to cross the border (the first escapee is probably going to take the free tag).
Exchange 2: Tag it (using a Fate Point if someone already used the free tag) for a +2 to your fire evocation, explaining that you are throwing the fire you tore out of the wall.