exceptionally bad follow-up service.

6 months ago they installed a new roll up garage door for us. After 5 months it started giving problems so I phoned and asked them to come and look at it. A month later I am still waiting for them to pitch up and I either get excuses or my messages are ignored whenever I ask what is going on. The job has a 6-mth warrantee and I'm now considering suing for breach of contract so I can use the money to get another company to come and do the job.