HTML Embed Form, sending wrong URL parameters

On the webiste we have a form where the customer can book a room by choosing date, guests and enter a promo code.
This form is linked up to their bookingsystem, and sends the inputs over and searches for available rooms.
All this works fine, except the promo code.

In the bookingsystem’s setup guide it gives this as the example to how to set up the promocode:
ratePlan=PROMO&promoCode=YourPromoCode

I’ve added this as the input field to be the promo code:

Promokode

When using a promo code, this is part of the URL:
ratePlan%3DPROMO%26promoCode=BWPCH3
And the promo code doesn’t work and won’t show the discounted price.

The URL should have been:
ratePlan=PROMO&promoCode=BWPCH3

So it seems that the signs for “=” and “&” gets replaced by “%3D” and “%26”.


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