Micromax — Application storage problem

Address:

Nagpur, Maharashtra

I had deposited my micromax mobile Canvas2 colors A120 in Al raza micromax service center in nagpur under Job sheet no - W[protected]. Micromax Canvas2 colors A120 & the problem is that phone has 8gb internal memory but its has three types of Storage option 1.PHONE STORAGE TOTAL SPACE IS 0.89GB 2.INTERNAL SD CARD TOTAL SPACE IS 5.28GB 3.EXTERNAL SD CARD TOTAL SPACE IS 14.73GB IS A 16GB SD CARD Now when I try to install app, its install in phone storage as it 0.89gb I can not install more than 2-3 apps and he get the storage full error. So i want to increase Application storage or merge this application storage with INTERNAL SD CARD.But they are unable to do so, they told me that"this is not happen" I am not satisfied by there answer they are very abusive in behaviour and not helpfull. so please my request.