You said 143Kbytes, which is about 1100Kbits, whereas they advertise 700Kbits for the home package and 1000Kbits for pro, if you have one of them then your getting over the speed they claim, so I couldn't see any reason to say it's slow.
if you meant 143Kbits, then yeah thats VERY slow and you should in that case get something done about it.
since I dont know which you mean, when you download a file does it go at 143k/sec on the transfer rate?