Pathetic service

I’ve bought a bed set in October 2020. Within the first 7 days I reported to House and Home that the stitching on the mattress was coming undone. Followed up with an email and photos to them. They’ve been giving me the round around ever since, indicating that they are waiting on feedback from their supplier. At the end of 2020 they told me that they bed would be replaced after 4 January 2021. I phoned them earlier last week only to find out that the mattress would be replaced sometime in February. I told them that this was unacceptable as they have a guarantee in place and that the bed should be replaced sooner. The person I spoke was going to get back to me. I am still waiting. Sent e-mail. No response. Any ideas as to what I can do next?