I have just been emailing a friend in Turkey and i said

"bu aksam seni ariyorum....this evening i will call you

he corrected me and wrote

"bu aksam seni arayabilirim".....does this mean this evening i will be able to call you.

was my first sentence correct?

1-This evening i will call you - Bu akşam seni arayacağım

2-This evening i will be able to call you - Bu akşam seni arayabileceğim.

*This second sentence is alittle bit tricky infact. The exact english translation is Bu akşam seni arayabiliyor olacağım.  However this is gramatically correct  no one would say that or you can use that in a very rare situation that i cannot think of right now.

*You can also say Bu akşam seni arayabilirim (This includes alittle bit of unsureness.) like bu akşam seni araya da bilirim aramaya da bilirim, if that  makes any sense.  Infact the context of the dialogue is what determines which one you would like to say.

3-This evening i am calling you-Bu akşam seni ariyorum.

So your first sentences tense is wrong. Hope this will help you...

Impulse, yardimin icin tesekkur ederim. I understand now.

But one more question....seni ariyorum....when would i use this phrase?

Seni ariyorum : You might use that when you have been searching for someone for a while.

Like:  Ne zamandır seni arıyorum. Nerelerdesin?  I have been looking for you for along while. Where have you been?

Some people also use it like they will be calling someone in a future time frame

Like this : O zaman yarın sabah seni ariyorum :  So, I will be calling you tomorrow morning.

But this is I think just what the everyday language is like.  Seni arıyorum is grammitcally means I am calling you. You can ofcourse also use it in a current time frame.

I hope that makes sense. (and i modified my first reply. dont forget to check it mate)

great reply. Thanks you have covered everything and more. A few more useful phrases under my belt.