Is there a way to convert a `.vcf.gz.tbi ` file back to a `.vcf.gz` or `.vcf` file?

My end goal is to convert these files into plink bed/bim/fam files, but plink will not accept the .vcf.gz.tbi file as is.  Any help is appreciated! 
No. An index (that is what tbi is) is just a table of content. You cannot reconstruct every page of a book with just the ToC at hand. 