Use much better wallets like electrum as suggested.
OP, take note of the above advice. Don't hate bitcoin because you're using a lousy wallet--bitcoin didn't jump out of a birthday cake with a gun pointed at your head to force you to download Coinomi. Just sayin'. And also as others have said, you haven't lost that $15 worth of
BTC as long as you wrote down the seed phrase.
And as far as the problem with Coinomi goes, I've had that issue before because I've used the wallet before....but not in a long, long time, and I don't remember exactly how I got the problem fixed. What I can say is that all is not lost and I have faith that you'll figure it out.
On the other hand, if you're going to attempt to send $15 worth of bitcoin to another address right now, be prepared to lose a decent chunk of that $15 in network fees. I'd suggest that if you absolutely don't need to send it immediately, wait until the network is less congested and it's cheaper to send small amounts. Now
that's not Coinomi's fault, it's a bitcoin thing that happens from time to time.