Following is a summary of your post:
a) You had been doing a certain type of work in the BPO industry. You say that you enjoyed it too. Over a period of time, you acquired expertise in your work.
b) Considering your expertise, your company has assigned higher-order work. This work is a logical extension of what you had been doing all along.
c) Notwithstanding the high-order work, there is no increase in the remuneration.
d) Your concern is over the change of industry. You have moved from BPO to IT.
Comments: - These are as below:
e) Getting a work of the higher-order is also an achievement. Please accept the offer. However, make sure that you are given a proper letter for the change of designation and also a Job Description (JD) of a new position.
f) Your company has committed an increase in remuneration. Please tell the authorities concerned to include this commitment when they issue the letter for the change of designation.
g) Nothing wrong per se if your industry has been changed. People are recruited based on their expertise and not necessarily on the industry. Secondly, IT and BPO are the overall allied industries. You are not moving from BPO to animal husbandry.
h) Even if the company gives a hike after a few months, keep watch on a suitable higher level position in some other companies. You must get remuneration that commensurates with your expertise. This will be possible when you get into a new company.
i) Overall I feel that you could get into a management role in the IT industry. Therefore, alongside, develop managerial competencies also.
All the best!