If you change the baud rate setting on your modem after you've created an account, the baud rate setting associated with that account does not change. Baud rates seem to be saved in three places - the default entry in wvdial.conf, the individual account entries in wvdial.conf and the ifcfg-ppp* files. It appears that changing the modem baud rate changes only the "Default" value in wvdial.conf which is not inherited by anything because all the specific account entries explicitly specify the baud rates that was the default when they were created. It took me many hours to figure out why outgoing ftp's were very slow on my machine - I had created the account before I configured the modem (which is natural enough since the account screen is shown first), so although everything looked OK on the rp3-conf screens looked OK, the wrong baud rate was being set by the pppd options. The only way I found to set this right was to manually edit the ifcfg-ppp and wvdial.conf files.
This should be fixed in the Raw Hide version (currently at 1.0.7), which will probably become an errata within a week or two. Please upgrade to it and see if it solves your problem.
Bug 8977 has been closed because last input from user on possible fix was in 2000. If you experience this problem in Red Hat Linux 8.0 above, please open a new ticket.