Consumer Court Related

I have engaged an interior vendor for my apartment work and he has taken 2 lakh initially and completed 80K value work and stopped the work stating there is some extra work etc however there are a proper agreement and drawings signed between two parties. I have enough proof to claim and I am sure it will be through if I go legally. Please let me know how can I initiate the case. I met one lawyer recently, he said we will have to send to legal notice first and then we have to get acknowledgment from the postman, post which only we can file the case seems. Wondering what if the other guy does not accept the letter we sent