Tethering one’s Nokia E5 to take advantage of the 4GB of Internet traffic included in AmaySIM’s $39.90 plan (for 30 days) is quite simple, once all of the knowledge is in place.
Switch your phone to “PC Suite” mode...
Press [Menu]...at which point a serial device appears when you plug it into your PC (in this case, a laptop running Natty Narhal Kubuntu) at /dev/ttyACM0.
Select [Ctrl. Panel]
Select [PC Suite]
Select [Back] until Menu closes
Now follow AmaySIM’s instructions:
Select [Ctrl. Panel]
Select [Access point]
Select [Packet data]
Enter amaysim Internet and press [OK]
Select [Internet] as the destination
Highlight [Optus Internet], press [Options] and select [Edit]
Ensure Data bearer is set to [Packet Data]
Select [Access point name]
Enter or change to internet and press [OK]
User name and Password should be left blank [set to None]
Ensure Prompt password is set to [No]
Ensure Authentication is set to [Normal]
Ensure Use access point is set to [Automatically]
Press Options and select [Advanced settings]
Ensure Network type is set to [IPv4]
Ensure IP address is set to [Automatic]
Ensure DNS addresses is set to [Automatic]
Ensure Proxy server address is set to [None]
Ensure Proxy port number is 
Press [Back] until you return to the main menu
Press [Options] and select [Settings]
Select [Access Point]
Press [Options] and select [Exit]
All well & good. Now (you will need to be SuperUser/root) make your /etc/wvdial.conf file look like this:
Modem = /dev/ttyACM0
Modem Type = USB Modem
Baud = 460800
New PPPD = yes
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Init3 = AT+cgdcont=1,"IP","internet"
Carrier Check = no
Dial Command = ATDT
Phone = *99#
Username = *
Password = *
Ask Password = 0
Auto Reconnect = yes
Stupid Mode = yes
ISDN = 0
Auto DNS = on
Check DNS = on
Check Def Route = on
Depending upon your Linux distribution, you may need to (as SuperUser) mark the pppd file as SUID. In my case, finding the executable file was done with which pppd & ensuring the setting with chmod u+s /usr/sbin/pppd.
You may need to make your user(s) members of the groups dialout & dip by (as SuperUser) editing the /etc/group file, then logging them out & back in.
As one of said users, type wvdial & press Enter. Ten seconds later, the world appears. The command “ping ii.net” is a simple way to verify that DNS & traffic are both afloat.