Unless your organism is prokaryotic you need to use an aligner which is aware of splicing, to map RNA-seq reads over introns. Examples of these are STAR, Tophat2 and HISAT2. In addition, SNP discovery is possible for RNA-seq, but it is not straightforward and not the most reliable technique for SNP discovery.
Try when you ask a question to be as informative as possible and don't forget to mention which organism you are working on!
In addition, I'm not sure
-B 0 is a good setting for bwa mem, but that's something else... (Unless you know what you are doing, stick with the default settings. A tool should have reasonable default settings so you don't have to think about tens of options.)