Bonds of SBI issued in 1994 to dematerialise

I have bonds of SBI issued in year 1994 with face value 1000rs which were to be matured in year 2004.How it can be dematerialized as someone pointed out that they were called off in year 1998.plz help me out

They were matured in 2004??

Actually it was called off by SBI in year 1998 before maturity

So, it doesn’t exist now, so it is like expired,how can we convert it to demat form?