How to counter an early a4 move

In this position and similar position types, how do i counter an early a4 move by white?

1. d4 c5 2. d5 e6 3. c4 exd5 4. cxd5 d6 5. Nc3 Nf6 6. a4

Usually you see a4 as a response to black playing a6, preventing b5. When white plays a4 prematurely, i'm wondering if there is a way to respond/punish as black.

The computer suggests eventually putting the knight on a6 (allowing white to take with the bishop and double up the pawns). This looks difficult to play as black.

Thanks for any tips

Well hold your a6 position to later on in the game don't be tempted with a5 and then make sure you're not castling into trouble just for the sake of castling xxx that's what I've learnt in my journey ,lately xxx

Sometimes the best way to punish someone is to just live well. White has reduced his options. Stick to the Benoni plan up a tempo in mainlines and your ability to castle before trouble starts will help you. Qe7, Re8 and Na6-Nb4 are ways to punish some of the lines as well as getting in Bg4 where you otherwise could not.

7.e4 8. f4 attack doesn't work anymore since there is no Bb5 because you are in time to castle

7.e4 bg7 8.Nf3 allows bg4 which is something white does not want to allow whereas going 8.Be2 to switch the move order walks into 8...Qe7!

8.Nge2 Qe7! 9.Ra3! Na6 10.Ng3 Nb4 11.Be2 h5! and this feels like white is getting less than he deserves although it is an interesting position

8.h3 is wasting too much time since black gets play on the e file with Re8

The weak b4 square makes Bd3 a bit less appealing since Na6 threatens Nb4 hitting the bishop

So we can say 7.e4 is not as good as usual. so
7.Nf3 Bg7 Nd2 0-0 e4 is the main line which again Na6-Nb4 is good in as an improvement to the regular move order.