Google adds old company name to some of our titles in SERP, how to avoid?

Hi,

Our company rebranded with a new name and a new website about 1/2 a year ago. Now we've noticed that for some results on SERP, Google has added our old company name at the end of the title. I would like to avoid this since it only causes confusion

Inspecting the page itself, the old company name is not in the title tag or anywhere else - so this is definitely something that Google adds by itself. It's added for totally new content as well, so it's not like the links was present on the old page. A post was added yesterday and now google has added our old name to the results.

Does anyone know how to deal with this or have any suggestions?