H1B transfer to old employer

[ntnmadan]

Hi all,
WHen I came to USA I was working for company A (petition valid and stamped till mayb2018), last year I got an approval from company B and joined them , I recently got an h1b transfer approval from company X , now company A is giving me a better offer which I am considering taking , I have not yet joined company X, can I join company A on the old petition and ge an extension initiated , or should I initiate a new h1b transfer ?
Any ideas on this
Thanks in advance