If the church is unwilling to help locally, you could try appealing to their regional leadership (though this is unlikely to work). From there, your next steps fall into 2 boxes:
Management Double-glazing, earplugs, white noise, etc.
Fighting back Rallying sympathetic neighbours sounds as though it's not an option, so to start with, you should familiarise yourself with any relevant ordinances - if you need professional legal advice, consider bringing your sympathetic neighbour in on it and split costs. Trolling - the Satanic Temple (not the church of Satan as others have recommended) or the Church of the Flying Spaghetti Monster are your best bet on getting pseudo-legitimacy, and may have intervened in similar situations. Sabotage - cutting cables is cheap and fun - audio, data, power - who knows what cable does what, but trial and error is an option - bonus points for attracting rodents and and outsourcing the job to them. If you want to get creative, a HERF gun may be a viable option. Pamphlet drops to the congregation with something along the lines of "love thy neighbour - with 120db bells at x, y, z times" - don't do this if you're making less ethical moves - you'll paint an obvious target on your back. If you can get access to the audio console, your effective options open right up - but this probably involves breaking and entering, so that's probably more inadvisable than the rest of my advice.