Then imposed another 2 year contract 

The old legacy box I presume? That was discontinued in January 2020, after which you need at least an HD box for Astro to work. It's presume it was due to Astro changing the encoding of it's DVB-S2 signal to AVC (h264) only, and stopped it's MPEG-2 SD broadcast. The old box are so old that it does not support h264.

Yes, by right you can do it only via phone or walk in to service centre.

Alternatively, you can file a MCMC complaint, say that you've tried contacting customer service and hold on the line for so long, yet no one attend you, which made your life difficult just to terminate Astro subscription. After that, they'll become kind hearted to assist your termination request right away.
Let's just say if other provider like Unifi also practice this way to make customers difficult to terminate its service, would you still say "This has to be illegal"?

It is nothing surprising that companies would hire more agent to attend sales/upgrade related enquires, rather than assign more agents to attend service termination enquiries.

Take to court get refund and also claim for hassle, stress, and leave taken 

Called to terminate line yesterday around 5pm... Was no.2 in q and had to wait around 5 mins...lady on the line was quick and courteous.. Just asked for account number, name, ic no and reasons for termination.... Offered RM20 discount for 2 years but informed her that already decided..... Bill payment by credit card auto debit so she confirmed again to cancel.... This took another minute or 2 Before ending I asked her for case number which she gave and she informed that last day would be 17th due to billing cycle.... This morning 8am received SMS confirming cancellation of credit card auto debit.... All in all not a bad experience... Just have to wait and see what happens on 18th

Will do tomorrow morning

Update on today's attempt to terminate astro
This time again agent want to delay but give earlier date on termination next week, asked to terminate on the spot but say cannot, report to mcmc after call.
Just now, complain department called using hotline and explain situation, say will terminate one day before billing date. Email to confirm this also received.

There's a new satellite TV service in town: