We started a business of selling Air Conditions, Furnaces and water heater etc. If the customer requires we arrange loan with interest form commercial bank for them and we do not charge any thing from our customers for this extra service. (This is not the part of our business still we have to assist them to secure our business) If we do not provide this service to our customer we will be loosing our customers please let me know is this Halal or Haram.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is not permissible for you to offer such service to the buyer nor guide him to it, nor help him to have it in any way even if you do not take a fee for that as Allaah Says (what means): {...but do not help one another in sin and transgression.}[Quran 5:2]

Moreover, the Prophet said: “Allaah has cursed the one who consumes Riba (i.e. usury or interest), the one who gives it to others, the one who records it and the one who witnesses it (its transaction).” He said: “All of them are equal in sin.” [Muslim] So, the curse also included the one who helps the two contracting parties involved in Riba.

Instead, you should seek permissible means of promoting your trade without resorting to what is forbidden or helping in it, so that Allaah will bless your trade.

Allaah Knows best.