If the modem supports V.32, understand that the modem will only go as high as 4800 or 9600 bps. However, if you purchase a V.32bis modem, you can expect to increase data throughput as high as 14,400bps. The data is not actually compressed, rather the data sent is increased in quantity. If you enable your modem's error-correction and data compression features, you can usually correct these problems. The error correction protocols will retransmit the corrupted data bytes.
Data compression speeds the transmission thereby reducing the possibility of error.
Configuring your modem can be one of the most frustrating ordeals you will go through. If it is configured incorrectly, it will not work. Many configuration routines can take place through the AT command set. If you are having difficulties with your modem, you can defer to the modem's documentation for the correct commands and parameters to correct the problems. Kimberly Maxwell has written hundreds of articles and several books relating to connectivity and communications.