problems after VOIP install

Recently changed from analog phone to voip (Comcast in MI) and fax/printer would no longer work. Attempted correction (only printing one page then spooling forever) and then lost MS Office suite (Excel, Word, Powerpoint) documents. Recovered MSOS docs and lost printer/fax functonality again. Any suggestions as to why? Dell MS and VOIP provider pointing finger at each other.