You welcomed them nicely, so what not do the same at the end of the call. Suitable for the end of IVR surveys or similar.
 
Please don't hesitate to drop me a line if your needs aren't met in the telephone message shop.
 
This is one of 4 call-end messages available in the shop. Others:
https://www.martinwhiskin.co.uk/product-page/call-end-message-2
https://www.martinwhiskin.co.uk/product-page/call-end-message-3
https://www.martinwhiskin.co.uk/product-page/call-end-message-4