Mobile handset has no service

I'm contracted to Telkom for a Samsung S6 handset which has been receiving sporadic reception from the start of it's 2 month inception. The situation has only worsened in the past seven days whereby I have had zero service.<br> <br> The call center has tried assisting me with zero positive outcome & now I cannot even contact them as my phone now gives the error message 'not registered on network'.<br> <br> I require desperate use of the phone for work especially during standby hours and I have to also keep in constant contact with an elderly parent.