How do we cancell a land line? what is the correct procedure?

The lazy way would be to stop paying your Telkom bill. They will likely contact you, then. Caution - make sure they don't cancel your new line. Also, one of your past Telkon bills should have a phone number for you to call customer service.

i don't know. you will need proof you own your number.
you may wish to consider 'porting' your land line number to another telephone provider. many are now 'porting'
[ moving ] land line numbers to cell telephones so they continue to receive all calls going to the previous land line.
please contact the telephone land line owner's business office understand their rules and termination fees if any.

Call your Carrier like AT&T

If you have Telkom, web sites can be found using https://www.google.com

Examples of search result:

https://www.thesouthafrican.com/news/how-to-cancel-your-telkom-phone-line-and-adsl-service-online/

https://secure.telkom.co.za/today/help/personal/faq/when-it-best-contact-telkom-customer-care-call-centre/

Contact your phone company.

This is FIXYA.

call telstra
go to a telstra shop go on line to telstra web site and fill out the form

nothing fixya site can do
send the hotel an e-mail cancelling the reservation
write a letter to the hotel cancelling the reservation