Hello!
We stopped selling the Gigaset DECT handsets as the entry level models were discontinued last year. The Yealink are similar and have a couple of advantages over the Gigaset (easier to transfer and support more SIP accounts & handsets per base station. (At home, I have on of each - a Gigaset for home use and a Yealink for work)
Time to update your web site, which still show the obsolete handsets.
I spoke to your sales person a week or two ago and was informed that the Gigaset solution was still what you provide, so maybe also time to ensure your staff are aware as well.