Either

I didn't intend to [either] increase or lower it.
I intended to neither increase nor lower it.

Huevo's offerings are surely correct, but I get the feeling there's a story here - that something happened, and this is your explanation, perhaps with a bit of irony:

"Right, I didn't intend to increase it, but I certainly didn't intend to lower it!"

"I didn't intend to increase it; neither did I intend to lower it."

Many versions are possible, depending on what you

Yes, exactly, this kind of irony I was trying express somehow. I know it is grammatically incorrect; I was trying omit repetitiveness.

Basically, what I was trying to say is : I didn't have any intention it increase the amount but it doesn't mean I would agree to lower it.

Hi, anon.
Actually, repetition is not always bad. Perhaps with two sentences, you can get closer to the effect you want:
I didn't intend to increase it. But I didn't intended to lower it either.
I didn't intend to increase it. But neither did I intend to lower it. / !

We often use "mean to" instead of "intend to" - a bit more casual.