[Serusers] Correcting SDP for Grandstream BT101

Hi! I'm using different kinds of hard-UAs, among them the Grandstream BT-101 and Siemens optiPoint 400 standard SIP. Grandstream sends the following rtpmaps out to the other party: <snip> a=rtpmap:0 PCMU/8000/3 a=rtpmap:8 PCMA/8000/3 a=rtpmap:4 G723/8000/3 a=rtpmap:18 G729/8000/3 a=rtpmap:2 G726-32/8000/3 a=rtpmap:15 G728/8000/3 a=rtpmap:99 iLBC/8000/3 a=fmtp:99 mode=20 a=rtpmap:9 G722/8000/3 </snip> and the Siemens phone always states "user agent incompatible" - seems as if its complaing about the appended "/3" of every rtpmap. Regarding the RFC the third parameter states the count of channels (?). With other UAs (XLite, Sipura) audio connection is possible. Anyway is there a possibility to correct this problem using ser? Can I issue a command that removes every /3 from the rtpmaps coming from th Grandstream phone? Alex Mack