Not solving the problem since 3 months

I have Vodafone Corporate Connection (9734247131), Sim & Handset both are 4g. I cant use 4G , everytime the network bar shows 3G or E(2G) After disconnecting every call the Network Vanishes for 1 min .Still i have replaced the 4G SIM twice and have done every step to satisfy customer care. After complaining 10 times (with complain no.) they are avoiding/ unable to solve the issue. They are not even bothered to solve the issue. Have Offered around 15-16 GB 4GB data but all in hail, cant have the speed to utilise it.